wandering eye pathophysiology

Lazy eye (amblyopia)

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Lazy eye (amblyopia) is reduced vision in one eye caused by abnormal visual development early in life. The weaker — or lazy — eye often wanders inward or outward.

Amblyopia generally develops from birth up to age 7 years. It is the leading cause of decreased vision among children. Rarely, lazy eye affects both eyes.

Early diagnosis and treatment can help prevent long-term problems with your child's vision. The eye with poorer vision can usually be corrected with glasses or contact lenses, or patching therapy.

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Signs and symptoms of lazy eye include:

• An eye that wanders inward or outward
• Eyes that appear to not work together
• Poor depth perception
• Squinting or shutting an eye
• Head tilting
• Abnormal results of vision screening tests

Sometimes lazy eye is not evident without an eye exam.

See your child's doctor if you notice his or her eye wandering after the first few weeks of life. A vision check is especially important if there's a family history of crossed eyes, childhood cataracts or other eye conditions.

For all children, a complete eye exam is recommended between ages 3 and 5.

Lazy eye develops because of abnormal visual experience early in life that changes the nerve pathways between a thin layer of tissue (retina) at the back of the eye and the brain. The weaker eye receives fewer visual signals. Eventually, the eyes' ability to work together decreases, and the brain suppresses or ignores input from the weaker eye.

Anything that blurs a child's vision or causes the eyes to cross or turn out can result in lazy eye. Common causes of the condition include:

• Muscle imbalance (strabismus amblyopia). The most common cause of lazy eye is an imbalance in the muscles that position the eyes. This imbalance can cause the eyes to cross in or turn out, and prevents them from working together.

Difference in sharpness of vision between the eyes (refractive amblyopia). A significant difference between the prescriptions in each eye — often due to farsightedness but sometimes to nearsightedness or an uneven surface curve of the eye (astigmatism) — can result in lazy eye.

Glasses or contact lenses are typically used to correct these refractive problems. In some children lazy eye is caused by a combination of strabismus and refractive problems.

• Deprivation. A problem with one eye — such as a cloudy area in the lens (cataract) — can prohibit clear vision in that eye. Deprivation amblyopia in infancy requires urgent treatment to prevent permanent vision loss. It's often the most severe type of amblyopia.

Factors associated with an increased risk of lazy eye include:

• Premature birth
• Small size at birth
• Family history of lazy eye
• Developmental disabilities

Untreated, lazy eye can cause permanent vision loss.

Aug 14, 2021

• Coats DK, et al. Amblyopia in children: Classification, screening, and evaluation. https://www.uptodate.com/contents/search. Accessed June 8, 2021.
• AskMayoExpert. Amblyopia. Mayo Clinic; 2021.
• Amblyopia. National Eye Institute. https://www.nei.nih.gov/learn-about-eye-health/eye-conditions-and-diseases/amblyopia-lazy-eye. Accessed June 8, 2021.
• Amblyopia preferred practice pattern. American Academy of Ophthalmology. https://www.aao.org/preferred-practice-pattern/amblyopia-ppp-2017. Accessed June 8, 2021.
• Coats DK, et al. Amblyopia in children: Management and outcome. https://www.uptodate.com/contents/search. Accessed June 8, 2021.
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Amblyopia (Lazy Eye)

At a glance: Amblyopia

Poor vision in 1 eye

Eye drops or wearing an eye patch

What is amblyopia?

Amblyopia (also called lazy eye) i s a type of poor vision  that usually happens in just 1 eye but less commonly in both eyes. It develops when there’s a breakdown in how the brain and the eye work together, and the brain can’t recognize the sight from 1 eye. Over time, the brain relies more and more on the other, stronger eye — while vision in the weaker eye gets worse.

It’s called “lazy eye” because the stronger eye works better. But people with amblyopia are not lazy, and they can’t control the way their eyes work.

Amblyopia starts in childhood, and it’s the most common cause of vision loss in kids. Up to 3 out of 100 children have it. The good news is that early treatment works well and usually prevents long-term vision problems.

What are the symptoms of amblyopia?

Symptoms of amblyopia can be hard to notice. Kids with amblyopia may have poor depth perception — they have trouble telling how near or far something is. Parents may also notice signs that their child is struggling to see clearly, like:

• Shutting 1 eye
• Tilting their head

In many cases, parents don’t know their child has amblyopia until a doctor diagnoses it during an eye exam. That’s why it’s important for all kids to get a vision screening at least once between ages 3 and 5.

Is my child at risk for amblyopia?

Some kids are born with amblyopia and others develop it later in childhood. The chances of having amblyopia are higher in kids who:

• Were born early (premature)
• Were smaller than average at birth
• Have a family history of amblyopia, childhood cataracts, or other eye conditions
• Have developmental disabilities

What causes amblyopia?

In many cases, doctors don’t know the cause of amblyopia. But sometimes, a different vision problem can lead to amblyopia.

Normally, the brain uses nerve signals from both eyes to see. But if an eye condition makes vision in 1 eye worse, the brain may try to work around it. It starts to “turn off” signals from the weaker eye and rely only on the stronger eye.

Some eye conditions that can lead to amblyopia are:

• Refractive errors. These include common vision problems like nearsightedness (having trouble seeing far away), farsightedness (having trouble seeing things up close), and astigmatism (which can cause blurry vision). Normally, these problems are easy to fix with glasses or contacts. But if they’re not treated, the brain may start to rely more on the eye with stronger vision.
• Strabismus . Usually, the eyes move together as a pair. But in kids with strabismus, the eyes don’t line up. One eye might drift in, out, up, or down.
• Cataract. This causes cloudiness in the lens of the eye, making things look blurry. While most cataracts happen in older people, babies and children can also develop cataracts.

How will my child’s doctor check for amblyopia?

As part of a normal vision screening , your child’s doctor will look for signs of amblyopia. All kids ages 3 to 5 need to have their vision checked at least once.

What’s the treatment for amblyopia?

If there’s a vision problem causing amblyopia, the doctor may treat that first. For example, doctors may recommend glasses or contacts (for kids who are nearsighted or farsighted) or surgery (for kids with cataract).

The next step is to re-train the brain and force it to use the weaker eye. The more the brain uses it, the stronger it gets. Treatments include:

Wearing an eye patch on the stronger eye. By covering up this eye with a stick-on eye patch (similar to a Band-Aid), the brain has to use the weaker eye to see. Some kids only need to wear the patch for 2 hours a day, while others may need to wear it whenever they're awake.

Putting special eye drops in the stronger eye. A once-a-day drop of the drug atropine can temporarily blur near vision, which forces the brain to use the other eye. For some kids, this treatment works as well as an eye patch, and some parents find it easier to use (for example, because young children may try to pull off eye patches).

After your child starts treatment, their vision may start to get better within a few weeks. But it will probably take months to get the best results. After that, your child may still need to use these treatments from time to time to stop amblyopia from coming back.

It’s important to start treating children with amblyopia early — the sooner the better. Kids who grow up without treatment may have lifelong vision problems. Amblyopia treatment is usually less effective in adults than in children.

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Lazy Eye (Amblyopia)

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Edward Kuwera, M.D.

What is amblyopia?

Lazy eye, also known as amblyopia, is one of the most common eye disorders in children. Lazy eye occurs when vision in one (or possibly both) of the eyes is impaired because the eye and the brain are not properly working together. This condition is sometimes confused with strabismus , also known as a misalignment of the eyes.

What is the risk of developing lazy eye?

Lazy eye is present in approximately 2% – 4% of the U.S. population. The risk of developing the condition increases if a child:

• Is born prematurely
• Experiences a development delay
• Has a family history of lazy eye

What causes lazy eye?

There are three known causes of lazy eye:

Strabismus : Known as strabismic amblyopia, a misalignment of the eyes causes the brain to ignore input from the askew eye in order to avoid the confusion of double vision in a young developing brain. This eye then experiences a drop off or total loss in visual acuity as the brain favors the eye that is straight.

Refractive errors : Known as refractive amblyopia, poor visual development is caused by a difference in the amount of refractive error between the eyes. Although the child may have correct eye alignment, he or she may experience substantial nearsightedness, farsightedness and/or astigmatism in one eye, while experiencing none of these symptoms in the other.

When this happens, the brain becomes dependent on the better eye, while largely ignoring the issues of the eye with more refractive error. This leads to a lack of use and amblyopia in that eye.

Obstruction of vision: Known as deprivation amblyopia, the obstruction of light from a child’s eye prevents the development of proper visual acuity. This can be caused by:

• Cataract (a cloudy lens)
• Droopy eyelid (ptosis)
• Corneal scar

How is lazy eye diagnosed?

Lazy eye is diagnosed through a routine eye exam. Your child’s first eye exam should take place between the ages of 6 and 12 months old. Pediatricians routinely screen for general eye problems.

Lazy Eye Signs and Symptoms

Signs and symptoms of lazy eye include:

• Misalignment of the eyes, or strabismus
• Poor depth perception and peripheral vision
• Repeated eye closure or squinting
• Eyes that don’t move in the same direction when the child is trying to focus.
• A persistent head turn or head tilt
• Persistent shaking of the eyes

Lazy Eye Treatment

Lazy eye is generally treated by forcing the nonworking eye to work more actively. Lazy eye should be treated in early childhood to prevent it from becoming permanent, but studies have shown that older children may also benefit from treatment.

The standard treatment method for lazy eye , an eye patch is placed on the stronger eye in order to restore the brain’s attention to the visual input from the weaker eye. This allows proper visual development to occur in the weaker eye.

Corrective lenses and glasses

When dealing with lazy eye from refractive errors, vision restoration can be achieved with vision correcting glasses or contact lenses. 

Atropine eye drops

Similar to the patch method, this treatment is administered in the form of eye drops into the stronger eye, which temporarily weakens its vision. This restores the connection between the brain and the weaker eye to strengthen its visual input.

This treatment involves constant dilation of the strong eye, which can bring about light sensitivity  and difficulty in clearly seeing near objects during treatment. This form of treatment is most useful for farsighted prescriptions.

Treatment of strabismic amblyopia often involves strabismus surgery to align the eyes. This surgery is typically followed by additional treatment methods such as the use of an eye patch on the stronger eye, atropine eye drops to the stronger eye, and/or eye therapy exercises to strengthen the weaker eye. In some cases, more than one strabismus surgery may be needed.

Treatment of deprivation amblyopia will usually require an operating room procedure, such as cataract surgery , droopy eyelid surgery or the surgical removal of corneal scars.

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Types of Amblyopia (Lazy Eye)

In this article

Amblyopia, commonly called lazy eye, is children’s most common type of vision impairment. 8 It causes poor vision in one eye due to improper visual development early in life. 

Various types of lazy eyes have different causes and treatment needs.

Types of Lazy Eye

There are three main types of lazy eye:

Strabismic Amblyopia

Strabismic amblyopia is the most prevalent type of lazy eye. This type occurs when one eye turns in or out.

Strabismus is a muscle imbalance that causes the eyes to cross in or turn out. When the eyes aren’t aligned, they don’t work together properly. 

Children with strabismus may develop amblyopia if the brain stops registering visual information from the misaligned eye.

Refractive Amblyopia

Refractive amblyopia occurs when the eyes have a significant difference in vision. 

This type of lazy eye is typically due to farsightedness (hyperopia) . However, it can result from other refractive errors , such as:

• Nearsightedness (myopia)
• Astigmatism

These vision problems are usually easy to fix with eyeglasses or contact lenses. Left untreated, the brain may favor the eye with better vision, leading to amblyopia.

Deprivation Amblyopia

This is usually the most severe type of lazy eye. Deprivation amblyopia is when a problem in one eye—such as a cataract—causes impaired vision in that eye. 

Although cataracts are common in older adults, infants with deprivation amblyopia require urgent treatment to prevent vision loss.

What Does Lazy Eye Look Like?

People with amblyopia have normal eyes, but the brain favors one eye. This may result in the eye looking off-center or drifting in one direction. 

As the brain continues to rely on one eye, vision in the other eye gets worse. Rarely, this can affect both eyes. Without treatment, it can lead to partial or total vision loss.

Development of amblyopia usually occurs between birth and 7 years of age. About 2% to 3% of people have amblyopia. 8

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What Causes Lazy Eye? 

Anything that interferes with normal vision during a child’s development can lead to a lazy eye. Amblyopia occurs when the brain begins ignoring visual signals from the eye with the worst vision.

Some children are at a higher risk of developing a lazy eye. These include children who have: 1

• A family history of amblyopia
• Developmental disabilities
• Complications at birth (including premature birth)

Several types of vision issues can cause a lazy eye:

Refractive Errors

Certain refractive errors can cause a lazy eye. They include:

• Nearsightedness (myopia). This refers to difficulty seeing objects at a distance.
• Farsightedness (hyperopia). This refers to trouble seeing things up close.
• Astigmatism. This refers to a curve in the cornea that causes blurred or distorted vision.

Childhood strabismus can lead to other eye problems like amblyopia. To avoid double vision, a child’s brain may ignore images from the misaligned eye. This prevents the eye from developing normal vision.

Physical Eye Problems

Any eye condition that causes reduced vision or vision loss in one eye can lead to amblyopia. Examples include:

• Childhood cataracts (congenital cataracts)
• Droopy eyelids (ptosis)
• Corneal ulcers
• Eye injuries
• Eye surgery

Symptoms of Lazy Eye

Unlike strabismus, amblyopia is difficult to notice with a simple observation. However, some signs may indicate amblyopia in children. 

Children with amblyopia may display poor depth perception by not knowing how near or far an object is. 

You may notice other signs that your child is having difficulty seeing clearly, such as:

• Squinting or shutting one eye
• Crossed eyes
• A droopy eyelid
• Bumping into objects
• Poor depth perception
• Tilting their head to one side
• One eye drifts in a different direction than the other

Most of the time, parents aren’t aware their child has amblyopia until a doctor diagnoses it during an eye exam. That’s why all children should have a vision screening by their fourth birthday.

How Is Amblyopia Diagnosed?

Your child’s healthcare provider or eye doctor will diagnose amblyopia with an eye exam. Early diagnosis is essential for successful treatment. Most pediatricians check children’s eyes during routine check-ups.

All children should have their vision checked by age 4. Your child’s eyes should be checked by a pediatric ophthalmologist during infancy if there’s a family history of eye problems, such as:

• Childhood glaucoma
• Congenital cataracts

Amblyopia treatment is most effective when started as early as possible. Constant suppression of signals from the lazy eye can lead to vision loss in that eye. After a child turns 8, the chances of vision improvement drop dramatically.

There are two approaches to amblyopia treatment:

• Addressing the underlying eye problem
• Training the lazy eye to work so it can develop normally

Treating Underlying Eye Problems

When amblyopia is due to a refractive error or physical eye problem, treatment may include:

Corrective Lenses

Sometimes, corrective eyewear is all it takes to treat amblyopia. Eyeglasses and contact lenses can correct refractive errors like:

• Nearsightedness
• Farsightedness

A child needs to wear their glasses or contacts consistently for the treatment to be effective.

Eye surgeries that may treat various types of amblyopia include:

• Cataract surgery. To remove a clouded lens and restore clear vision.
• Eyelid surgery. To treat a droopy eyelid.
• Strabismus surgery. To correct eye alignment.

Training the Lazy Eye

There are several ways to train a lazy eye. Here are four options:

Your child may cover the better-seeing eye with a patch to stimulate the weaker eye, making it stronger over time. They wear the eye patch for 2 to 6 hours daily or more.

Bangerter Filter

This special filter is an alternative to an eye patch and achieves the same goal of stimulating the weaker eye. A Bangerter filter fits over the eyeglass lens of the dominant eye.

Atropine eye drops cause temporary blurry vision in the stronger eye. Similar to using a patch or filter, this approach encourages using the weaker eye.

Side effects of atropine include eye irritation and sensitivity to light.

Vision Therapy Exercises

Vision therapy exercises like eye movement control and strengthening techniques can help strengthen vision in the weaker eye.

The outlook for amblyopia depends on how early treatment begins—the sooner, the better.

Without treatment, a lazy eye can worsen. If the brain continues suppressing images from the lazy eye, permanent vision loss may occur. 

Treatment before age 8 is necessary to provide the best chances of preserving a child’s vision.

Can You Prevent Amblyopia? 

Some lazy eyes are preventable. If your child has strabismus or a structural eye problem, you may be able to treat it before it leads to amblyopia.

In other cases, treatments like eye drops or eye patches can help strengthen the weaker eye. But the lazy eye might always be slightly weaker than the other.

Amblyopia, or lazy eye, occurs when the nerve pathways between the brain and eye don’t develop properly in childhood. 

Amblyopia is very common, especially if you have a family history of eye problems. Having one weaker eye can cause blurred vision and other issues.It is important to treat amblyopia as early as possible. An early childhood eye exam can diagnose this condition.

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Amblyopia (Lazy Eye)

Division of ophthalmology, what is amblyopia.

Amblyopia, also known as lazy eye or wandering eye, is a common vision problem in children. In most cases of amblyopia, your child’s brain ignores the signals coming from one eye, meaning the other eye is the only one being used.

Over time, the brain gets used to working with only one eye. The eye that’s being ignored by the brain doesn’t develop normal vision.

If treated while your child is young and the eyes are still developing, he has a good chance of overcoming amblyopia. The goal of treatment is to make your child’s brain use both eyes. Getting the eyes to work as a team becomes harder as your child grows. Early treatment is best; and treatment may not work at all if started after 7-10 years of age.

If left untreated, amblyopia may keep your child from developing normal vision.

Amblyopia affects 2-5 percent of children.

Amblyopia has three main causes:

• Strabismus , which occurs when a child’s eyes aren’t aligned (straight). The eyes don’t work together. This leads the brain to ignore one eye.
• Refractive error , or need for glasses. Children are especially at risk if one eye has larger need for glasses compared to other eye.
• Conditions that cause poor vision in one eye, like cataract or droopy eyelid (ptosis), which prompts the brain to ignore the blurry pictures seen by that eye.

Additional factors can place a child at a higher risk for amblyopia, including:

• A family history of amblyopia
• Prematurity
• Developmental delay
• Craniofacial disorders
• Certain genetic conditions, such as Down syndrome (trisomy 21) , 22q deletion syndrome , Williams syndrome and Noonan syndrome

Symptoms of amblyopia can vary from child to child, but may include:

• Squinting in one or both eyes
• Rubbing one eye (not just when tired)
• Holding items close to the eyes to see them
• A wandering or crossed eye (strabismus)

It’s important to note that some children display no symptoms of amblyopia. The child’s strong eye — and her brain — can compensate for the weaker eye, making it appear that the child has good vision.

Testing and diagnosis

Vision screening is the best way to detect presence of amblyopia or risk factors for developing amblyopia. Photoscreening, a type of vision screening that uses a special camera to determine how well a child can see, is often performed in conjunction with vision testing at pediatricians or schools.

The goal of treatment for amblyopia is to:

• Correct the problem that is causing amblyopia
• Make each eye see as well as it can, which often involves forcing the brain to use the “weak” eye
• Force the brain to use the signals from both eyes
• Make both eyes work together

Amblyopia is most often treated by blocking one eye to keep it from doing all the work. The brain can learn to accept signals from the eye that’s being ignored. Gradually, vision in this eye may improve.

Commonly used treatments include:

• An eye patch  is placed over the eye that’s being used. With this eye blocked, the brain is forced to start working with the eye it’s ignoring. The patch must be worn while your child is awake. Your child may not like wearing a patch. But remember that treatment will work only if your child wears the patch as often as instructed.
• Medicated (atropine) eye drops  can be used instead of a patch. Drops are put in the “good” eye, blurring near vision in that eye. This allows the eye that’s being ignored to start working with the brain. Eye drops may be an option for certain children who don’t like wearing a patch. But putting in eye drops can take practice.
• Eyeglasses can help correct focusing problems . They can also be prescribed to blur sight in the eye that’s being used. This forces the brain to work with the eye it’s ignoring. In some cases, sight in one eye is blocked by sticking a patch or a filter to the inside of an eyeglass lens. As vision improves, your child’s eyeglass prescription may change.

Follow-up care

Once amblyopia improves, maintenance treatment may be needed to prevent vision from slipping. Maintenance treatment includes continued wearing of eyeglasses and/or wearing an eye patch for decreasing amounts of time during the day than was required during the treatment period.

Amblyopia can cause blindness, but fortunately it is the most reversible cause of blindness. Treatment is highly successful as long as children and families stick to the treatment plan.

Reviewed by Stefanie L. Davidson, MD

Providers Who Treat Amblyopia (Lazy Eye)

William Anninger, MD

Gil Binenbaum, MD, MSCE

Stefanie L. Davidson, MD

Emily A. DeCarlo, MD

Brian j. forbes, md, phd.

Anne Jensen, MD

Priyanka Kumar, MD

Ayesha Malik, OD

Monte D. Mills, MD

Julia E. Reid, MD

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• Continuing Education Activity

Amblyopia is a visual disorder due to the failure of cortical visual development in one or both eyes due to ocular pathology early in life. Consequences of amblyopia include poor stereovision, visual acuity, pattern recognition, and low sensitivity to motion and contrast. This activity reviews the evaluation and management of amblyopia and explains the role of the interprofessional team in improving care for patients with this condition.

• Describe the etiology of amblyopia.
• Summarize the epidemiology of amblyopia.
• Identify the ocular examination used in the evaluation of amblyopia.
• Review the importance of collaboration and communication among the interprofessional team members to enhance the delivery of care for patients affected by amblyopia.
• Introduction

Amblyopia is a disorder of the development of sight. It is due to the failure of cortical visual development in one or both eyes from ocular pathology early in life. Often, amblyopia is referred to as a "lazy eye" by the general public. Amblyopia results in permanent decreased vision in the pathological eye if not treated early enough, even if the ocular pathology is removed later on in life. It is the most common cause of decreased vision in a single eye among children and younger adults.

Amblyopia occurs early in life when the developing visual system fails to transmit a sharp image to the visual cortex. Amblyopia can be the result of media opacities, cataracts, strabismus, or anisometropic refractive errors that place one eye at a developmental disadvantage to the other. Amblyopia usually occurs unilaterally but can occur bilaterally with cataracts of both eyes or high refractive errors. Our visual experience as infants and children determines how we see as adults. [1] [2] [3]

Amblyopia is diagnosed by identifying diminished visual acuity in one or both eyes that are out of proportion to the structural abnormality of the eye, excluding any other visual disorders as the underlying cause. It can be defined as an interocular difference of two lines or more in acuity when the refractive error is corrected. In young children, visual acuity can be difficult to measure but can be estimated by observing the reactions of the child when one eye is covered, including watching the child's ability to follow objects with one eye.

Amblyopia can be broken down into three main causes: deprivation, strabismus, and refractive. Deprivation amblyopia comes from any pathology that inhibits the visual pathway. This could be a cataract, corneal opacity, damage to the retina, or optic nerve pathology. It can even be caused by the absence of visual stimuli, such as covering one eye or living in complete darkness. Deprivation causes the most severe form of amblyopia. Strabismus is when both eyes do not align. The pediatric brain prevents diplopia by suppressing the visual input in one eye, leading to impaired visual development in that eye. [4] The strabismus can be treated with surgery or prism glasses; however, amblyopia often persists despite treating the underlying strabismus. Refractive amblyopia stems from blurred visual input from hyperopia, astigmatism, or myopia. Generally, an eye with hyperopia or astigmatism has a higher likelihood of developing amblyopia than myopia, as a myopic eye will still have near objects in focus.

Typically the more profound the visual deprivation, the more severe the resultant amblyopia will be. The critical period for visual development is roughly the first seven years of life, with the first few years and even months being the most critical. [5] The later the amblyopia treatment begins, the more difficult it becomes to reverse clinically. This is because early-onset visual deprivation results in permanent anatomic changes in the magnocellular (M) and parvocellular (P) visual pathways. For this reason, surgeons may need to operate on dense congenital monocular cataracts very early, often within a week after discovery. Even a few months with a congenital cataract could lead to irreversible amblyopia. With binocular, equally dense congenital cataracts, there is a little more flexibility, usually a few weeks. [6] [7]

• Epidemiology

In its various forms, amblyopia has historically been cited to affect up to 3% of the population, with a 1.2% lifetime risk of vision loss from this condition. [8]  More recently, the global prevalence of amblyopia has been cited to be around 1.75%. [9]  Anisometropia was the most common cause of amblyopia, followed by mixed anisometropia and strabismus, strabismus, and visual deprivation. The diagnosis for mixed and strabismic amblyopia is typically made at an earlier age (7.4) than anisometropic amblyopia (12.7). [10]  The prevalence of amblyopia appears to be equal between right and left eyes. No sex predilection has been found. 

• Pathophysiology

With monocular visual deprivation during visual development, there is competition between the neural networks of the two eyes for impact on cortical neurons. Different aspects of neuronal selectivity, such as synaptic plasticity, activity-dependence, and neuronal network learning, have different sensitive periods and are therefore affected differently by the types of vision deprivation involved.

It is the anatomic relationships of photoreceptors to ganglion cell receptor fields, ganglion cell receptor fields to the layers in the lateral geniculate, and the lateral geniculate to the layers of the visual cortex that determine amblyopia. The age of onset and duration of the disability determines its depth. The earlier the onset and the longer it goes untreated, the harder amblyopia is to correct. [11]

• History and Physical

A thorough medical history of the patient should be queried all the way back to childhood. Medical records should be obtained if it is still possible to get them. Important questions to ask include when did decreased vision in the suspected eye start and does the patient has any history of refractive correction, ocular trauma, ocular pathology, amblyopia treatment, and ocular surgeries. Sometimes the patient may be unaware of this history, so getting the history from the parents on family members may be of help.

Any patient with suspected amblyopia should have a complete eye exam. The visual acuity of each eye should be checked individually with the patient’s refractive correction. Visual acuity may be overestimated in amblyopic eyes when using individual visual targets, so it may be beneficial to bracket the visual targets for accuracy. [12] Steroacuity testing should be performed, as amblyopic eyes often have impaired or absent stereopsis. [13] All patients with decreased vision should have refraction done. In children, this often should be done after cycloplegia to get cycloplegic refraction and uncover underlying hyperopia. [14] The pupillary reflex should be tested with light, and the eye in question should be assessed closely for a relative afferent pupillary defect using the swinging flashlight test. [15]  The intraocular pressure (IOP) should be checked in all patients that are able to undergo the testing. Sometimes this testing is deferred in patients that have difficulty undergoing the testing, especially children. [16] Extraocular motility and confrontational visual fields should be assessed in all patients that are able to do this testing. Tropias and phorias should be assessed with the cover-uncover test and alternate cover test. This can uncover any underlying strabismus, a common cause for amblyopia. [17] All patients with suspected amblyopia should undergo a dilated exam. When examining the eyes, special attention should be paid to the ocular structures involved in vision: the cornea, lens, retina, and optic nerve.

Further testing that should be considered when evaluating for amblyopia includes formal visual field testing, optical coherence tomography (OCT), fundus photography, and an electroretinogram (ERG). [18] Brain and orbit imaging can be considered if there is suspicion for a compressive lesion along the visual pathway. Amblyopia is a clinical diagnosis, and additional patient testing should only be done to evaluate for other ocular pathology causing decreased vision. Brain magnetic resonance imaging (MRI) in research has shown decreased visual cortex size in patients with amblyopia. [19] [20] [19]  However, MRI is not recommended as a diagnostic test for amblyopia. 

• Treatment / Management

The initial treatment of amblyopia depends on the underlying cause. Deprivation amblyopia should first be treated by removing the obstructive pathology. This may be cataract surgery, retinal detachment repair, corneal surgery, or treatment for a variety of other ocular pathologies. Refractive amblyopia often is the most amenable to treatment. Treatment of the patient’s entire refractive error with corrective lenses may be treatment enough to reverse the amblyopia. In strabismic amblyopia, strabismus repair may realign the eyes; however, this rarely is enough to reverse amblyopia completely.

All forms of amblyopia often need to utilize visual penalization of the non-amblyopic eye to force visual development in the amblyopic eye. The most common form of visual penalization is patching the non-amblyopic eye. The amount of time the non-amblyopic eye is patched per day varies with the severity of the amblyopia. Practitioners often patch for two hours, six hours, or sometimes even full-time. [21]  Visual activity such as reading, watching television or playing video games while patching may be helpful, as the patient will be forced to use the amblyopic eye and may be more cooperative with the patching if it is associated with an enjoyable activity. Patching of the non-amblyopic eye as a treatment for amblyopia began in the 16th century. It remains the mainstay of therapy to this day. [22] [23] If the patient cannot reliably go through patching therapy, pharmacologic amblyopia treatment is an option. A cycloplegic drug (usually atropine) can be used to inhibit accommodation in the non-amblyopic eye. The benefit of this therapy includes ease of putting in one drop daily compared to having to maintain a patch over the eye for hours at a time. This therapy has been found to have similar effectiveness to patching in the correct patients. [24] However, patients who are myopic or emmetropic in the non-amblyopic eye may not benefit from pharmacologic therapy since these eyes will maintain the focus of objects at certain distances.  

The older the patient gets, the more likely the plasticity of the brain to reverse amblyopia is no longer present. The exact age at which amblyopia treatment becomes futile is not uniformly agreed upon. However, The Pediatric Eye Disease Investigator Group found that patients from seven to twelve showed at least some benefit from amblyopia treatment, compared to patients thirteen and older, who showed minimal improvement with treatment. [25]

• Differential Diagnosis

Amblyopia is a diagnosis of exclusion, meaning that amblyopia can only be diagnosed when all other ocular or cerebral pathology has been ruled out as the cause for decreased visual acuity. Common causes of decreased visual acuity include refractive error, cataract, corneal pathology, retinal pathology, and optic nerve pathology. Most of these pathologies can be ruled out by a complete eye exam. Cerebral visual impairment and functional (non-organic) vision loss should also be considered. [26]

The prognosis of amblyopia is dependent if it is treated at an early age and the severity of amblyopia. Amblyopia has significant morbidity and is a common cause of monocular decreased vision. At least 75% of children treated with occlusion therapy do show a good return of vision. However, in at least 50% of children, there is a slight decrease in visual acuity over time. The best outcomes are in children who are referred early in life. However, in many cases, the actual real-life images may be slightly altered in many children as they grow. [27] [28]  However, if treated, more than 70% of patients have significant vision improvement within 12 months. Even after treatment, there may be some decline in vision over the coming years. Risk factors for failure to restore vision include age at which treatment for the condition started (later treatment tends to have a worse outcome), deprivation amblyopia, and poor initial visual acuity.

• Complications

The main complication of amblyopia is an irreversible, lifelong decrease in vision. These visual functional abnormalities include reductions in visual acuity, contrast sensitivity, vernier acuity, spatial distortion, abnormal spatial interactions, and impaired contour detection. Patients with amblyopia will have binocular abnormalities such as impaired stereoscopic acuity and abnormal binocular summation. The monocular vision deficits are usually specific to only the amblyopic eye. However, subclinical deficits of the non-amblyopic eye have also been demonstrated.

People with amblyopia have difficulty seeing three-dimensional images hidden in stereoscopic displays such as autostereograms. Perception of depth, however, from monocular cues such as size, perspective, and motion parallax in the non-amblyopic eye typically remains normal.

Learning may also be impaired in children with amblyopia. Children with amblyopia read and answer multiple-choice questions slower than children that do not have amblyopia. [29] [30]  Another possible complication of amblyopia includes worsening strabismus due to impaired binocular fusion.

• Deterrence and Patient Education

Parents should be educated on the importance of early vision exams for their children. School vision screenings may be the first time amblyopia is suspected. If a child has been diagnosed with amblyopia, parents should be educated that if untreated, the vision loss from amblyopia is typically irreversible. The importance of treatment should be emphasized with the parents. Children may not want to wear glasses or patches, but parents need to ensure that their child goes through with the treatment. Providers should encourage parents at every visit to continue treatment, as amblyopia treatment may need to continue for a long period of time.

• Pearls and Other Issues

Amblyopia or lazy eye is a disorder of sight due to the eye and brain not working together. It results in decreased vision in an eye that may appear normal. It is the most common cause of decreased vision in a single eye among children and younger adults. In practice, the earlier the onset of its sensitive period, the more profound the visual deprivation and the deeper the resultant amblyopia. Refractive amblyopia is typically the most amenable to treatment, especially astigmatic amblyopia. Sometimes refractive correction alone may be all that is needed for treatment. If the amblyopia does not resolve, then patching the non-amblyopic eye is indicated.

• Enhancing Healthcare Team Outcomes

Pediatric ophthalmologists are typically the physicians who treat amblyopia, although optometrists also have experience in treatment. It is critically important that the patients are referred to a provider that has training in amblyopia treatment because mismanagement of this condition can lead to irreversible vision loss. The first provider to suspect amblyopia often will not be an ophthalmologist or optometrist. It may be a pediatrician, family doctor, nurse, or medical assistant. Family members spend more time with the patients and may be the first to notice preferential fixation of the non-amblyopic eye. Many cases of amblyopia will be caught during vision screenings. These screening programs are critical to catching amblyopia early. [31]  [Level 5] Without an appropriate referral, the child is at risk for permanent vision loss. The longer the condition remains undiagnosed and untreated, the poorer the outcome. Health care providers need to communicate effectively with other providers as well as parents to prevent irreversible vision loss from this condition.

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left esotropia therefore amblyogenic condition amblyopia confirmed by poor fixation UCUSUM Contributed by Gerhard Cibis, MD

Disclosure: Kyle Blair declares no relevant financial relationships with ineligible companies.

Disclosure: Gerhard Cibis declares no relevant financial relationships with ineligible companies.

Disclosure: Arun Gulani declares no relevant financial relationships with ineligible companies.

This book is distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0) ( http://creativecommons.org/licenses/by-nc-nd/4.0/ ), which permits others to distribute the work, provided that the article is not altered or used commercially. You are not required to obtain permission to distribute this article, provided that you credit the author and journal.

• Cite this Page Blair K, Cibis G, Gulani AC. Amblyopia. [Updated 2023 Aug 8]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-.

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• Long-term changes in visual acuity and refractive error in amblyopes. [Optom Vis Sci. 2004] Long-term changes in visual acuity and refractive error in amblyopes. Rutstein RP, Corliss DA. Optom Vis Sci. 2004 Jul; 81(7):510-5.
• Review Developmental vision disorders: Do children and adolescents benefit from active vision training? IQWiG Reports – Commission No. HT21-03 [ 2023] Review Developmental vision disorders: Do children and adolescents benefit from active vision training? IQWiG Reports – Commission No. HT21-03 . 2023 Jul 25
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• 1.1 Definition
• 1.2 Etiology
• 1.3 Risk Factors
• 1.4 General Pathology
• 1.5 Pathophysiology
• 1.6 Primary prevention
• 2.1 History
• 2.2 Physical examination
• 2.4 Symptoms
• 2.5 Clinical diagnosis
• 2.6 Diagnostic procedures
• 2.7 Laboratory test
• 2.8 Differential diagnosis
• 3.1 General treatment
• 3.2 Medical therapy
• 3.3 Medical follow up
• 3.4 Surgery
• 3.5 Surgical follow-up
• 3.6 Complications
• 3.7 Prognosis
• 4.1.1 Objectives
• 4.1.2 Design
• 4.1.3 Main outcome measures
• 4.1.4 Results
• 4.1.5 Limitations
• 4.1.6 Conclusions
• 4.1.7 Pearls for clinical practice
• 5 Additional Resources
• 6 References

Disease Entity

Amblyopia is a relatively common disorder and a major cause of visual impairment in children. It represents an insult to the visual system during the critical period of development whereby an ocular pathology (ex. strabismus, anisometropia, high refractive error, or deprivation) interferes with normal cortical visual development. Approximately 3-5% of children are affected by amblyopia. [1]

Amblyopia represents diminished vision occurring during the years of visual development secondary to abnormal visual stimulation or abnormal binocular interaction. It is usually unilateral but it can be bilateral. The diminished vision is beyond the level expected from the ocular pathology present.

Bilateral amblyopia is less common than unilateral amblyopia. Bilateral cases are caused by bilateral image blur (anterior visual pathway). Examples of etiologies for bilateral amblyopia include bilateral media opacities (including corneal opacities, infantile or childhood cataracts, or vitreous hemorrhages), or ametropia (bilateral high astigmatism or high hypermetropia). Unilateral causes of amblyopia also include the same types of media opacities seen in bilateral cases. However, the most common causes of unilateral amblyopia are strabismus and anisometropia, or a combination of the two [2] [3]

The etiologies of amblyopia can be easily remembered with the following mnemonic: S.O.S. Spectacles (anisometropia or high myopic or hyperopic refractive error), Occlusion (media opacities, retinal disease, optic nerve pathology, corneal disease, etc.), and Strabismus.

Risk Factors

A positive family history of strabismus, amblyopia, or media opacities would increase the risk of amblyopia in the child. Children who have conditions that increase the risk of strabismus, anisometropia, or media opacities (including Down syndrome) would also be at increased risk for the development of amblyopia. The risk of developing amblyopia, from a condition that is known to cause amblyopia, diminishes as the child approaches 8-10 years of age. As a corollary to this, the depth of amblyopia is typically less severe the older the child is at the time of onset of the amblyogenic factor.

General Pathology

In cases of bilateral amblyopia, the basic pathology is a significant blurred retinal image in each eye causing a disruption of normal visual development. This disruption must occur during the critical period of visual development (the first 8-10 years of life). The depth of damage depends on the severity of the blur, the length of time of the abnormal vision, and the age of onset of the insult. The pathology involved in unilateral amblyopia can be twofold. Retinal image blur in one eye can inhibit cortical activity from one eye, preventing normal visual development. Alternatively, misaligned eyes can prevent the normal process of fusion from taking place. This can result in suppression of the deviating eye, diminishing the acuity of the eye, and loss of binocularity. Sensory amblyopia is more severe than strabismic or anisometropic amblyopia and is tough to treat.

Pathophysiology

Abnormal visual stimulation during the critical period of visual development results in brain damage. Structural and functional damage occurs in the lateral geniculate nucleus and the striate cortex of the visual center in the occipital lobe in the form of atrophy of connections, loss of cross-linking between connections, and loss of laterality of connections.

Primary prevention

The key to prevention is detection. There are numerous techniques to detect amblyopia, all with varying degrees of specificity, sensitivity, complexity, and cost. These include a complete ophthalmic examination, photoscreening, visual evoked potentials, acuity charts, and tests of stereopsis and binocular function. Children who are at higher risk for amblyopia should be watched closely for early signs of this condition. In general, the quicker amblyopia is detected and addressed, the less negative effect it has on the visual system. Vision screening is advocated on the state level to screen as many children as possible for this disease prior to the age of kindergarten. Early intervention results in better overall vision. This is why the American Association for Pediatric Ophthalmology and Strabismus , the American Academy of Pediatrics , and the American Academy of Ophthalmology all support pre-kindergarten vision screening for children .

Amblyopia should be considered as a possible diagnosis in children with asymmetric visual behavior or acuity. It can also complicate the course of children with strabismus, or unilateral ocular or adnexal pathology such as a cataract, eyelid capillary hemangioma, or corneal scar. Bilateral amblyopia can also occur and should be thought of when a bilateral ocular condition occurs and despite treatment, some degree of diminished acuity persists. A careful history, thorough physical examination, and knowledge of possible etiologies of amblyopia can help the clinician to diagnose this condition.

Parents will often bring their child to the Ophthalmologist because of the underlying cause of the amblyopia (ptosis, strabismus, leukocoria, eyelid hemangioma), without realizing that amblyopia is present. In fact, anisometropic amblyopia usually goes undetected until picked up by a vision screening. The overwhelming majority of children with unilateral amblyopia do not complain of decreased acuity because they do not notice it unless one eye is occluded. The history taking process should include any family history of vision problems (specifically amblyopia and strabismus). Parents should be asked if the child was premature, and if they have ever noted any eye misalignment. Any prior testing (including school or Pediatrician vision screening, neuroimaging) should be noted. If any abnormality in the child's visual behavior has been noted, the duration is important. Also, some children may already have received care for amblyopia somewhere else. If this is the case, type of treatment and duration should be determined. Old records can be helpful.

Physical examination

Examination should consist of the following:

• Acuity testing (age appropriate): Single optotypes (without crowding bar) are not recommended as a good acuity testing technique in amblyopes because this test will tend to underestimate the degree of amblyopia (crowding phenomenon).
• Record the power of any current spectacles
• Subjective refraction if age appropriate
• Tests of stereopsis and binocular function (including Worth 4 dot testing, TNO stereo test)
• External examination (looking for ptosis, lid hemangioma or other lesion which could affect visual development)
• Presence or absence of an afferent pupil defect [4]
• Anterior segment examination (looking for any media opacity, or irregularity)
• Motility and ocular alignment
• Funduscopic examination
• Cycloplegic retinoscopy

The presence or absence of signs of amblyopia would depend on what the underlying etiology for the amblyopia is. Deprivational amblyopia could manifest with ptosis, an eyelid hemangioma, or a cataract for example. Strabismic amblyopia may show a constant or intermittent ocular deviation. Esotropia causes more amblyopia as compared to exotropia since esotropia is constant and exotropia is usually intermittent in nature. Anisometropic amblyopia often shows no obvious signs when observing the patient, but cycloplegic retinoscopy will reveal the anisometropia. On clinical examination, unilateral amblyopia will show asymmetric visual behavior or acuity testing results (although not all patients with asymmetric acuity have amblyopia). Severe cases may have a mild afferent pupillary defect. The crowding phenomenon is important to be aware of when testing visual acuity in an amblyope. The amblyopic eye of these patients will visualize individual letters better than a whole line of letters. Therefore, if the visual acuity tester uses individual letters (without crowding bar), then they may underestimate the degree of amblyopia that is present or miss it entirely. A neutral density filter significantly reduces vision in organic disease, but generally does not in pure amblyopia.

Patients with unilateral amblyopia are often asymptomatic. Occasionally, patients will complain that one eye is blurry, or younger children may report discomfort in the affected eye. Torticollis occurs infrequently. Poor depth perception or clumsiness may be noted.

Clinical diagnosis

In cases of unilateral amblyopia, the diagnosis requires two components. First, the patient must have a condition that can cause unilateral amblyopia. Examples would include strabismus, anisometropia, or a deprivational cause (ptosis, cataract, etc.). Second, the patient must have residual asymmetric acuity beyond the level expected from the underlying condition or that persists after treatment of the underlying condition. For example, a child with anisometropic hyperopia receives proper spectacle correction. Acuity in the more hyperopic eye improves but is still below that of the less hyperopic eye. This asymmetry of acuity represents amblyopia. In cases of bilateral amblyopia, a condition must be present during the critical years of visual development which produces constant, significant visual blur. Examples of such conditions would include bilateral vitreous hemorrhages, bilateral cataracts, bilateral corneal pathology, bilateral high hypermetropia, or bilateral high astigmatism.

Diagnostic procedures

A normal, comprehensive ophthalmic examination is usually all that is necessary to diagnose amblyopia. Components of this examination include (but are not limited to): acuity testing, cycloplegic refraction and retinoscopy, tests of stereopsis and binocular vision, evaluation of pupillary responses, anterior segment examination, cover-uncover and alternate-cover testing, and dilated funduscopic examination. See the Physical Examination section above.

Laboratory test

Laboratory testing is not a typical feature of amblyopia diagnosis. Certainly if the etiology of the amblyopia was unclear, or if vision was deteriorating despite treatment, neuroimaging would be considered. Fundus dystrophies (specifically Stargardt disease) may have normal appearing fundus in early stages with unexplained vision loss. Such patients may need fundus photo, fluorescein angiogram, optical coherence tomography of macula, and electrophysiological tests. Patients with high astigmatism may need corneal topography to rule out keratoconus.

Differential diagnosis

There are cases of decreased acuity in children in which amblyopia is not present. Ocular pathology or refractive error (or even improper spectacle correction) may cause decreased acuity without any superimposed amblyopia. Prechiasmal lesions or optic nerve insult can also produce unilateral decreased acuity.

Although there is much practitioner variability in the treatment of amblyopia, the general idea is to first treat the underlying cause for the amblyopia. Examples of this treatment would include prescribing glasses for anisometropia, strabismus surgery or spectacles to eliminate strabismus, or removal of a unilateral cataract to eliminate the media opacity. In unilateral or asymmetric cases of amblyopia, if there is a residual visual deficit after the underlying etiology is treated then amblyopia is said to exist. This can be addressed with occlusion therapy, pharmacologic therapy, or some other less commonly used modalities. Much of the data on the success of various treatment modalities for amblyopia through the years has come from retrospective, single site chart-review type studies. Over the last decade, there has been an explosion of amblyopia research. The need for prospective randomized trials in the treatment of amblyopia has begun to be met by the Pediatric Eye Disease Investigator Group (PEDIG) . This is an NEI-funded network including both University-based and community-based clinicians. The power of such a group lies in its ability to conduct multiple trials in a cost-effective fashion, with simple protocols implemented as part of routine practice [5] . Patients are enrolled at multiple clinical sites in a prospective randomized fashion, with standardized visual testing protocols [6] .Important data derived from these studies is present throughout this section on amblyopia.

General treatment

The key to optimal treatment of amblyopia is early detection and intervention. In symmetric bilateral cases, treatment consists of addressing the etiology of the diminished vision. Often there is residual bilateral amblyopia which may improve over time [7] . In asymmetric cases or unilateral cases, active treatment with patching, pharmacologic agents, or some less commonly used modalities can often improve the residual visual deficit.

Medical therapy

In anisometropic patients, some improvement in amblyopia can occur with glasses alone. Starting treatment in this manner may lessen the burden of subsequent amblyopia therapy for those with denser levels of amblyopia and in some cases may obviate the need for patching or pharmacologic penalization. Patching of the sound eye to improve the acuity of the amblyopic eye is the most commonly used technique to treat amblyopia. Patching compliance is a major concern, with high rates of poor compliance or noncompliance in some studies. Compliance with therapy can be bolstered by parental education and improving parental attitudes towards patching therapy. The number of prescribed patching hours per day varies widely between practitioners. In general most doctors recommend heavier patching regimens for worse degrees of amblyopia. The thought behind this is that heavier patching would improve results and the rapidity of obtaining them. However this practice has been called into question by recent PEDIG studies.

A study of severe amblyopes randomized the patching regimen to 6 hours of prescribed patching per day versus 12 hours per day. At the 4-month outcome visit, acuity improvements and rapidity of improvement were essentially identical between the groups [8] . A similar study of moderate amblyopes comparing 2 hours of prescribed patching per day to 6 hours per day, also found no difference in results [9] . Some clinicians also prescribe 'near activities' in conjunction with patching but this was not found to be beneficial in a recent study [10] .

Pharmacologic penalization of the sound eye is another commonly used modality to treat amblyopia. Atropine is the most commonly used pharmacologic agent. Dosing can be a drop in the sound eye daily, or on weekends only. A recent study showed results with weekend-only dosing to be similar to daily dosing for moderate amblyopes [11] . In children who wear hyperopic spectacles, atropine usage is sometimes combined with replacing the hyperopic lens over the sound eye with a plano lens. This was felt to 'enhance' treatment,  but a recent study showed only a minimal benefit of this additional step in therapy [12] .A common assumption is that atropine use in the amblyopic patient can only be effective if it induces a fixation switch. This assumption has been called into question by a recent study. Often the decision whether to treat the amblyopic child with patching or pharmacologic agents, is based on the practitioner's practice patterns and parental wishes.

A head-to-head study showed that 6 hours a day of patching therapy produced a slightly more rapid and beneficial effect than daily instillation of Atropine 1%, in moderate amblyopes younger than 7 years of age. However, the final difference at 6 months was not statistically significant and a parental questionnaire showed families preferred pharmacologic therapy over patching [13] .

Other modalities of medical amblyopia management include optical penalization with an occlusive Bangerter filter placed on the glasses lens or the use of a high plus lens to blur the sound eye, as well as contact lenses used as occlusion or for blurring.

Dichoptic video games and dichoptic movies are being studied as potential novel therapies for amblyopia. PEDIG studies showed that patching was superior to the use of an earlier, less engaging, dichoptic falling blocks video game for amblyopia treatment [14] [15] . More recently, PEDIG showed that in children aged 7 to 12 years who received previous treatment for amblyopia other than spectacles, the dichoptic adventure video game Dig Rush showed no benefit to vision or stereoacuity after 4-8 weeks of treatment over spectacle use alone. [16]

A novel digital therapeutic using virtual reality (VR) headsets, Luminopia One, delivers dichoptic amblyopia therapy while providing an engaging patient experience. Therapeutic visual stimuli are presented using real-time modification of patient-selected, cloud-based video content (e.g., television shows or movies) within a head-mounted display. In a randomized clinical trial of 105 children aged 4-7 years across 21 sites with anisometropic or strabismic amblyopia, amblyopic eye visual acuity improved by 1.8 lines in the Luminopia One treatment group compared to 0.8 lines in the spectacles-alone control group. [17] On 2021 October, the FDA approved Luminopia One for "improvement in visual acuity in children with amblyopia, aged 4-7, associated with anisometropia and/or with mild strabismus,"

CureSight is a promising dichoptic treatment for amblyopia that uses eye-tracking to induce real-time blur around the fellow eye fovea in dichoptic streamed video content. CureSight (90 min/day, 5 days/week) was found to be non-inferior to patching (2 hours/day, 7 days/week) in a 16 week multicenter trial of 103 children 4 to < 9 years with anisometropic, small-angle strabismic or mixed-mechanism amblyopia. [18]

Medical follow up

Follow up during treatment is typically somewhere between every 1-3 months. When treatment is discontinued, follow-up is necessary to ensure there is no regression of effect [19] .

Amblyopia itself is not a surgical condition, but there are times when surgery may treat the underlying cause of the amblyopia. Refractive surgery may be used to correct anisometropia. However, refractive surgeries are not approved by the Food and Drug Administration (FDA, USA) below 18 years of age. Eye muscle surgery can correct strabismus. Cataract, ptosis, vitrectomy, or corneal surgery may alleviate causes of deprivation.

Surgical follow-up

Even though surgery may be performed to alleviate some of the etiologies of amblyopia, most cases will still require follow-up to treat the amblyopia that is present. For example, in a child with strabismic amblyopia, eliminating the ocular misalignment does not automatically fully correct the amblyopia which resulted from the strabismus.

Complications

Overly aggressive amblyopia therapy (especially in younger patients) can produce reverse amblyopia of the sound eye. A new strabismus or a decompensation of an existing strabismus can also occur. Patches can be irritating to the skin, and the skin underlying the patch can become hypopigmented relative to the rest of the facial skin. There is also a potential social stigma associated with wearing the patch to school in some cases. Atropine use can cause side effects related to the use of this medication: flushing, rapid heart rate, mood changes (uncommon) and photophobia (common) would be examples of side effects occurring with the use of this medication. Reverse amblyopia can also occur with Atropine use as can decompensation of existing strabismus or development of a new strabismus. Cases of reverse amblyopia are infrequent and usually mild. Most cases resolve with discontinuation of treatment.

The keys to treatment success are younger age at detection/treatment, short course until intervention, and compliance with treatment. The effectiveness of intensive screening protocols to detect amblyopia at a young age has been shown to result in a better acuity of the amblyopic eye at age 7.5 years. Most patients do improve with treatment, but often residual amblyopia remains. With cessation of amblyopia treatment there is a risk of recurrence. In one study, the risk of recurrence was higher with better visual acuity at the time of cessation of treatment, a greater number of lines improved during the previous treatment, and a prior history of recurrence. Orthotropia or excellent stereoacuity at the time of patching cessation did not appear to have a protective effect on the risk of recurrence. In a prospective study of cessation of treatment in children aged 3 to <8 years with successfully treated amblyopia due to anisometropia, strabismus or both, the risk of amblyopia recurrence was found to be 24%. Patients treated with 6 to 8 hours of daily patching had a 4-fold greater odds of recurrence if patching was stopped abruptly rather than when it was reduced to 2 hours per day prior to cessation. Careful and prolonged follow-up during the amblyogenic years, is needed for all children who have been previously treated for amblyopia to prevent a recurrence. In general, the younger amblyopes are treated, the better the likelihood of improvement.

Most textbooks do not recommend trying amblyopia therapy in the second decade of life but some improvement can be obtained in few cases. A study of amblyopia therapy in children aged 7-17 years found that amblyopia improves to some degree with optical correction alone in about one fourth of patients. However most required additional treatment for amblyopia [20] . For patients aged 7 to 12 years, 2 to 6 hours per day of patching with near visual activities and atropine improved visual acuity even if the amblyopia had been previously treated. For patients 13 to 17 years, improvement was only noted in those children who had not been previously treated. The degree of improvement in these older children was much more modest than results from other studies of younger children, so the importance of early detection and treatment remains.

Studies have demonstrated that amblyopic children read significantly more slowly than controls, even when the vision in the amblyopic eye is only reduced to 20/30 vision. [21] [22] Amblyopia can also impact academic related fine-motor outcomes, such as multiple-choice answer completion time. [23]

Pertinent clinical trials

Pediatric eye disease investigators group study (pedig) –or– amblyopia treatment study.

Arch Ophthalmol 2002;120:268 | Arch Ophthalmol 2003;121:603 | Ophthalmol 2003;110:2075 | J AAPOS 2004;8:420 | Arch Ophthalmol 2005;123:437 | Ophthalmol 2006;113:895 | Ophthalmol 2006;113:904.

The goal was to determine if correcting the refractive error alone can treat amblyopia, the benefits of patching, and the risks of recurrence after suspension of treatment. In addition, it wanted to know until what age can amblyopia be treated and the management with atropine and occlusion.

This trial tried to facilitate an evidence-based approach to the treatment of amblyopia.

Clinical trials involving

• Observational study of spectacles alone for anisometropic amblyopia.
• Amblyopia treatment randomized to daily atropine to the fellow eye or at least 6 hours of patching per day.
• 2 concurrent randomized trials of patching, prescribed 2 hours/day versus 6 hours/day for moderate amblyopia and prescribed 6 hours/day versus full-time for severe amblyopia.
• Patching in older children: children randomised to receive optical correction ± patching for near activities.
• Recurrence of amblyopia: children treated with patching or atropine for at least three months with at least three lines of improvement were brought off therapy, and followed up for one year.

Moderate amblyopia was defined as 20/40 to 20/80. Severe amblyopi a was defined as 20/100 to 20/400. Successful treatment was defined as the improvement of VA to within one line of the non-amblyopic eye. Recurrence of amblyopia was defined as a reduction in at least two lines after cessation of amblyopia therapy or when treatment was restarted at an investigator’s discretion.

Inclusion criteria were children less than seven years, BCVA in the better eye better than 20/40, and the amblyopic eye less than 20/40. Previous refractive error corrected for at least four weeks before the study.

Main outcome measures

Primary endpoint: BCVA.

More than 4000 subjects have participated in 19 Amblyopia Treatment Studies (ATS). The main ones were:

• Observational study of spectacles alone for anisometropic amblyopia: 84 children, 3 to 6 years of age and VA from 20/40 to 20/250 at enrollment. 77% of the children improved at least 2 lines, and 27% showed resolution within 1 line of the fellow eye. Maximum improvement was achieved by 83% of subjects by 10 weeks, but some children improved for 30 weeks. Improvement was found in children with moderate and severe amblyopia. The key lesson was that spectacles are an effective initial tool in managing amblyopia.
• Amblyopia treatment randomized to daily atropine to the fellow eye or at least 6 hours of patching per day. 419 children, 3 to 6 years of age with amblyopia 20/40 to 20/100. VA improved in both groups at 6 months; during the initial treatment phase, the patching group did improve more quickly, but the atropine group caught up by 6 months. Thus, atropine and patching are effective in the treatment of amblyopia. Parental questionnaires found atropine to be better tolerated in terms of social stigma and compliance. The amblyopia treatment benefit persisted through age 10 years without a mean VA loss, but residual amblyopia remains in a large proportion of children. The mean amblyopic eye VA at 10 years was approximately 20/32, with 46% of amblyopic eyes 20/25 or better. After the initial 6-months, children were treated at the investigator's discretion with occlusion or atropine, and more than 85% of children continued to be prescribed treatment. So, amblyopia treatment is not a short-term task; it represents a long-term effort.
• 2 concurrent randomized trials of patching, prescribed 2 hours/day versus 6 hours/day for moderate amblyopia and prescribed 6 hours/day versus full-time for severe amblyopia in 3 to 6-year-olds children. 175 severe amblyopes were randomised to receive full-time patching vs. six hours/day patching for four months. 189 moderate amblyopes were randomised to receive either two or six hours a day of patching for four months. VA improved with both patching regimens without differences. Therefore, it is reasonable to initiate therapy with a lower dose and increase treatment intensity if the response is not good.
• Patching in older children: 507 children with amblyopia aged 7 to 18 were recruited and randomised to receive optical correction ± patching for near activities. There was a significant improvement in BCVA in those treated with patching in the 7-12 age group but not in the 13 -17 age group. When only the 13-17-year olds with no previous treatment for amblyopia were considered, there was an improvement in the patched group.
• Recurrence of amblyopia: 156 children who had been treated with patching or atropine for at least three months with at least three lines of improvement were brought off therapy at the investigator's discretion and followed up for one year. The average age was 5.9 years, and no child was older than eight. 21% of children experienced amblyopia recurrence, with 40% occurring within the first five weeks.

Limitations

Children younger than three were not included

Conclusions

Refractive correction alone may be effective in the treatment of amblyopia. There is no benefit in patching moderate amblyopes for longer than two hours and severe amblyopes for more than six hours per day. Children need close follow-up after discontinuation of occlusion therapy. There may be a benefit in treating amblyopia until 12 years of age. Teenagers with amblyopia who have never before received treatment may benefit from a trial of patching. There is no clinical difference in using atropine vs. patching in moderate amblyopes.

Pearls for clinical practice

Refraction helps amblyopia.

Moderate amblyopes can be treated using atropine or patching.

Additional Resources

• AAPOS Frequently Asked Questions about Amblyopia
• Prevent Blindness America - Amblyopia
• Boyd K, Puente MA Jr. Amblyopia . American Academy of Ophthalmology. EyeSmart/Eye health. https://www.aao.org/eye-health/diseases/amblyopia-6 . Accessed November 17, 2022.
• Boyd K, Lipsky SN. Depth Perception . American Academy of Ophthalmology. EyeSmart/Eye health. https://www.aao.org/eye-health/anatomy/depth-perception-2 . Accessed November 17, 2022.
• Boyd K, Puente MA Jr. Lazy Eye (Amblyopia) . American Academy of Ophthalmology. EyeSmart/Eye health. https://www.aao.org/eye-health/diseases/lazy-eye-amblyopia . Accessed November 17, 2022.
• Boyd K, Puente MA Jr, Turbert D. Strabismus (Crossed Eyes) . American Academy of Ophthalmology. EyeSmart/Eye health. https://www.aao.org/eye-health/diseases/strabismus-in-children-2 . Accessed November 17, 2022.
• ↑ Backman H. Children at risk of developing amblyopia: When to refer for an eye examination. Paediatr Child Health . 2004;9(9):635-637. doi:10.1093/pch/9.9.635
• ↑ Wright KW and Spiegel PH. Pediatric Ophthalmology and Strabismus. 1st ed. pp 195-229. 1999.
• ↑ Magdalene D, Bhattacharjee H, Choudhury M, Multani PK, Singh A, Deshmukh S, Gupta K. Community outreach: An indicator for assessment of prevalence of amblyopia. Indian J Ophthalmol [serial online] 2018 [cited 2018 Sep 2];66:940-4. Available from:  http://www.ijo.in/text.asp?2018/66/7/940/234966
• ↑ Simakurthy S, Tripathy K. Marcus Gunn Pupil. [Updated 2023 Feb 22]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK557675/
• ↑ Bacal DA. Amblyopia Treatment Studies. Curr Opin Ophthalmol. 15:432-436. 2004.
• ↑ Holmes JM, Beck RW, Repka MX, et al. The amblyopia treatment study visual acuity testing protocol. Arch Ophthalmol 2003, 119:1345-1353.
• ↑ Pediatric Eye Disease Investigator Group. Treatment of bilateral refractive amblyopia in children three to less than 10 years of age. Am J Ophthalmol 2007;144(4):487-96.
• ↑ Pediatric Eye Disease Investigator Group. A randomized trial of prescribed patching regimens for treatment of severe amblyopia in children. Ophthalmology 2003;110:2075-2087.
• ↑ Pediatric Eye Disease Investigator Group. A randomized trial of patching regimens for treatment of moderate amblyopia in children. Ophthalmology 2003;121:603-611.
• ↑ Pediatric Eye Disease Investigator Group. A randomized trial of near versus distance activities while patching for amblyopia in children aged 3 to less than 7 years. Ophthalmology 2008;115(11):2071-8.
• ↑ Pediatric Eye Disease Investigator Group. A randomized trial of atropine regimens for treatment of moderate amblyopia in children. Ophthalmology 2004;111(11):2076-85.
• ↑ Pediatric Eye Disease Investigator Group. Pharmacologic plus optical penalization treatment for amblyopia: results of a randomized trial. Arch Ophthalmol 2009;127(1):22-30.
• ↑ Pediatric Eye Disease Investigator Group. A randomized trial of atropine vs. patching for treatment of moderate amblyopia in children. Arch Ophthalmol 2002;120(3):268-278.
• ↑ PEDIG, Holmes JM, Manh VM, Lazar EL, et al. Effect of a Binocular iPad Game vs Part-time Patching in Children Aged 5 to 12 Years With Amblyopia: A Randomized Clinical Trial. JAMA Ophthalmol. 2016 Dec 1;134(12):1391-1400.
• ↑ PEDIG, Manh VM, Holmes JM, Lazar EL, et al. A Randomized Trial of a Binocular iPad Game Versus Part-Time Patching in Children Aged 13 to 16 Years With Amblyopia. Am J Ophthalmol. 2018 Feb;186:104-115.
• ↑ PEDIG, Holmes JM, Manny RE, Lazar EL, et al. A Randomized Trial of Binocular Dig Rush Game Treatment for Amblyopia in Children Aged 7 to 12 Years. Ophthalmology 2019 Mar;126:456-466.
• ↑ Luminopia Pivotal Trial Group, Xiao S, Angejeli E, Wu HC, et al. Randomized Controlled Trial of a Dichoptic Digital Therapeutic for Amblyopia. Ophthalmology 2022 Jan;129:77-85.
• ↑ Wygnanski-Jaffe T, Kushner BJ, Moshkovitz A, Belkin M et al, on behalf of the CureSight Pivotal Trial Group. An Eye-Tracking–Based Dichoptic Home Treatment for Amblyopia, A Multicenter Randomized Clinical Trial. Ophthalmology 2023;130:274-285.
• ↑ Pediatric Eye Disease Investigator Group. Risk of amblyopia recurrence after cessation of treatment. J AAPOS 2004;8(5):420-8.
• ↑ Pediatric Eye Disease Investigator Group. Randomized trial of treatment of amblyopia in children aged 7 to 17 years. Arch Ophthalmol 2005;123(4):437-47.
• ↑ Kelly KR, Jost RM2 De La Cruz A, Birch EE. Amblyopic children read more slowly than controls under natural, binocular reading conditions. J AAPOS. 2015 Dec;19(6):515-20.
• ↑ Kelly KR, Jost RM, De La Cruz A, et al. Slow reading in children with anisometropic amblyopia is associated with fixation instability and increased saccades. J AAPOS. 2017 Dec;21(6):447-451.
• ↑ Kelly KR, Jost RM, De La Cruz A, Birch EE. Multiple-Choice Answer Form Completion Time in Children With Amblyopia and Strabismus. JAMA Ophthalmol. 2018 Aug 1;136(8):938-941.
• Williams C, Northstone K, Harrad RA, et al. Amblyopia treatment outcomes after screening before or at age 3 years:followup from randomized trial. BMJ 2002; 324:1549-1551.
• Pediatric Eye Disease Investigator Group. Patching vs atropine to treat amblyopia in children aged 7 to 12 years: a randomized trial. Arch Ophthalmol 2008;126(12):1634-1642.
• Pediatric Ophthalmology/Strabismus

2021 Update: Lazy Eye and Adults

Lazy eye is estimated to affect up to 5% of all adults.

For many decades, it has been thought that only children under the age of 10 could be successfully treated for amblyopia (lazy eye). In other words, lazy eye treatment was usually not provided to children older than nine.

However, the National Eye Institute (NEI) recently funded a study that found that lazy eye can be successfully treated at least up to age 17 and even adults!

Now, lazy eye can be effectively treated in high school and college student and even adults !

What is lazy eye?

Lazy eye, also known as amblyopia, is a neuro-developmental vision condition that is caused when one eye is unable to achieve normal visual acuity or does not allow the full development of 3D vision.

A lazy eye typically affects the vision or visual function of the affected eye, causing blurred vision which contributes to poor depth perception and binocular vision.

Amblyopia may develop due to other vision conditions such as a wandering or crossed eye (strabismus), or unequal vision in the two eyes caused by nearsightedness, farsightedness or astigmatism.

Contact an eye doctor near you who can diagnose and treat your lazy eye.

Symptoms of lazy eye

Common symptoms of lazy eye:

• One or both eyes may wander inward or outward
• Both eyes may not seem to be working together
• Poor depth perception
• Squinting or shutting one eye in order to see
• Tilting one’s head in order to see
• Frequent eye strain, eye fatigue, or headaches

If you experience any of these symptoms, contact an eye doctor near you who diagnoses and treats lazy eye.

Schedule an appointment with a vision therapy eye doctor to help improve your visual skills .

SEE RELATED: New Research for Adults with Lazy Eye

Find a Vision Therapy Eye Doctor Near You

Are eye exams important.

Yes, frequent eye exams are essential as the earlier a lazy eye is detected, the higher the chances of successful treatment.

In many cases, amblyopia is detectable during a comprehensive eye exam. In addition, if there is a family history of lazy eye, it is crucial that your eyes be examined regularly, as lazy eye can be an inherited condition.

Specific tests are used during eye exams to assess both the visual acuity and the visual skills of each eye. This enables your eye doctor to diagnose a condition such as lazy eye.

Adult lazy eye treatment

For many years it was believed that amblyopia was only treatable in children, often those who are 10 years of age or younger. However, this isn’t necessarily the case. While every patient is different, many adults can see results from amblyopia treatment.

The visual system which consists of the brain, eyes, and visual pathways, can be retrained due to the brain’s plasticity.

For amblyopia , specifically, binocular vision needs to be retrained, as this is the root cause behind a lazy eye. 

With poor binocular vision the two images that the eyes see cannot be combined into one single image, but due to the plasticity of the brain, this does not have to be permanent.

While treatment is most effective when it’s given at an early age, it is still possible at any age to retrain the visual system, restore binocular vision, and correct amblyopia.

Lazy eye and vision therapy

Vision therapy is an effective treatment method for amblyopia. It has been shown to greatly improve the visual skills of the lazy eye by re-training the visual system.

Through vision therapy, the two eyes will be trained to work together to achieve clear and comfortable binocular vision.

Some vision therapy programs that treat amblyopia work to improve these visual skills:

• Accommodation (focusing)
• Fixation (visual gaze)
• Pursuits (eye tracking)
• Saccades (switching eye focus, “eye jumps”)
• Spatial skills (eye-hand coordination)
• Stereopsis (3-D vision)

LEARN MORE: Guide to Vision Therapy for Adults

Schedule an eye exam and vision evaluation for a proper diagnosis of lazy eye and to discuss whether a vision therapy program is the appropriate treatment for you.

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Amblyopia Surgery: Everything You Need to Know

• When It's an Option

How to Prepare

• What to Expect

Amblyopia (lazy eye) is a condition in which one eye does not function properly. Therefore, the brain only works with the better-seeing eye and ignores images from the weaker eye. Its symptoms include unequal vision in the eyes and impaired depth perception. This results in permanently decreased vision in the ambylopic eye that is not correctable with glasses or contact lenses.

Non-surgical interventions are more common than surgery for managing the causes of amblyopia. However, when appropriate, surgery can help to correct some of the causes in children. These can include strabismus (crossed eyes), cataracts, refractive errors, and a droopy eyelid.

This article discusses when surgery is an option for amblyopia. It also covers the purpose of surgery, what to expect, and recovery.

When Is Surgery an Option for Amblyopia?

Surgery may be an option for certain eye conditions that cause amblyopia. However, surgery doesn't treat amblyopia itself.

The most common treatments for amblyopia are wearing glasses or an eye patch. These can help your weaker eye learn to work in coordination with the brain. If you have surgery to fix a condition that causes amblyopia, you may still need to wear glasses or a patch afterward for a certain amount of time.

Conditions Treated With Surgery

The following lists some eye conditions that may lead to amblyopia and what surgeries may be used to correct them. Most of these procedures are minimally invasive with a small incision, and some are done with laser surgery. General anesthesia or monitored anesthesia sedation with local anesthesia are required to prevent the child from moving during the procedure.

Refractive Vision Impairments

Sometimes, a refractive vision impairment such as myopia (nearsightedness) , hyperopia (farsightedness) , or astigmatism can cause amblyopia. This can happen if the vision defect affects only one eye, or if it affects both eyes unequally.

Vision correction might reverse amblyopia, especially if done at a young age. However, most cases of refractive correction in children can be treated with glasses and occasionally contacts.

Surgery is generally reserved for children with anisometropic amblyopia who do not respond to standard treatment. Anisometropic means that there is a large difference in prescription between the two eyes.

Surgery may also be used with children with serious vision impairment who are unable to wear glasses for developmental, sensory, or other reasons. As a result, only a small percentage of children are suitable candidates for this surgery. When surgery is needed, photorefractive keratectomy (PRK) is more commonly performed on children than LASIK ( laser-assisted in situ keratomileusis ) surgery. That's because PRK doesn't have certain risks that LASIK has.

With PRK, the ophthalmologist uses a laser to shape the cornea. This helps improve how the light focuses on the retina to correct vision.

Strabismus Strabismus , or crossed eyes, can sometimes cause amblyopia. In strabismus, your eyes are pointed in two different directions. For instance, one eye may be focused straight ahead, while the other is turned to the inside.

To avoid double vision, your brain then focuses on the eye that sees straight ahead and ignores the other eye, This keeps the weaker eye from developing correctly, leading to amblyopia.

Eye muscle surgery may be recommended for treating strabismus. This surgery is performed on the muscles to realign the eye. It works by tightening the eye muscles (resection procedure) or loosening the eye muscles (recession procedure).

In a recession procedure, the eye muscle is detached and reattached further from the front of the eye so the muscle is weaker. In a resection procedure, the eye muscle has a section removed to make it shorter and stronger.

Cataracts Cataracts are a clouding of the eye's lens. It not only affects adults, but it can occasionally affect children, too. It may be something they're born with or something they develop in childhood.

Without treatment for cataracts, vision distortion can lead to amblyopia. That's because children's eyes and brains are still developing in their ability to process vision.

In this case, the first step to resolving amblyopia is cataract surgery . The procedure involves removing the cloudy lens in your eye and replacing it with an artificial lens.

Afterward, most children need ongoing treatment to help improve the connections between the brain and eyes. They may need to wear an eye patch, glasses, or contact lenses. Droopy eyelid

Droopy eyelid, also called ptosis , is when the upper eyelid droops over the eye and blocks your vision. In some cases, it can cause amblyopia, since one eye can see better than the other.

Ptosis surgery involves tightening the levator muscle, which lifts the eyelid. It might also involve attaching the eyelid to other muscles that can help lift it.

After surgery, amblyopia is treated by using an eye patch, special eyeglasses, or eye drops to help the weaker eye get stronger.

Contraindications

While useful for these eye issues, surgery is not recommended for all types of vision defects that cause amblyopia. For example, if the visual defect is caused by dysfunction of the brain's occipital lobe (the primary vision area), surgery will not correct it.

Health issues like a bleeding disorder, inflammatory disease, or immune dysfunction can increase your risk of complications. You and your healthcare provider will have to weigh the risks and benefits of surgery in your case.

An acute illness or infection can be a contraindication to surgery and will need to resolve before the procedure can proceed.

Potential Risks

In addition to the standard risks associated with surgery and anesthesia, these ophthalmic surgeries have certain potential complications.

Problems that may occur due to surgery include:

• Structural damage to the eye

These complications might require immediate intervention. If not adequately resolved, an adverse surgical event may result in a lasting vision issue that could be worse than the original problem.

Blurry vision, decreased vision, or blindness are potential rare and unforeseen complications in any ophthalmic surgery.

Purpose of Surgery

Amblyopia is the leading cause of vision impairment in children. Surgery, along with follow-up treatment, can help relieve the following effects of amblyopia:

• Decreased vision in one or both eyes
• Misaligned eyes (one eye turned inward)
• Head tilting
• Impaired depth perception 

Symptoms of amblyopia are not always obvious. In fact, many people with amblyopia do not complain about vision difficulties or eye movement issues. Often, amblyopia is diagnosed with a routine eye examination, such as a refraction test .

The American Academy of Ophthalmology suggests that children should have their eyes examined and vision tested as newborns, before age 1, and again before age 3.

Addressing amblyopia as early as possible is important. Early treatment can prevent permanent vision loss later in life. Vision deficits in amblyopia can occur due to several mechanisms that change the way the brain processes visual information:

• When vision is better in one eye, the brain may adapt and preferentially use the better eye, ignoring the eye with impaired vision. When one eye is not used, vision declines further and eye alignment may be impaired as the weaker amblyopic eye starts to drift.
• Asynchronous eye movements can cause blurred or double vision. The brain suppresses one of the images by favoring one eye. This causes the vision to decline in the other eye.

The first goal of all amblyopia treatment is to improve the vision with refractive corrective wear if possible. Many times, a lens prescription (refractive correction) will restore proper eye alignment.   

Surgery may be necessary to correct structural defects in the eye. However, even with surgery, follow-up treatment is typically needed to correct amblyopia. This involves strengthening your weaker eye by increasing its use.

One example is patching. Wearing a patch over the good eye forces the brain to start using the weaker eye so it can become stronger. As an alternative, prescription eye drops are sometimes used to blur the vision in the stronger eye for the same purpose.

If surgery is recommended, the ophthalmologist (eye surgeon) will plan the procedure based on observation of the eyes. This may include an eye examination , eye muscle testing , tests for depth perception, and imaging tests such as a computerized tomography (CT) scan .

Specific testing might be needed to evaluate issues like congenital cataracts .

You and your healthcare provider will discuss the necessary correction, as well as whether the surgery will be done with a laser. There are several types of laser eye surgeries, such as laser-assisted surgery for cataracts . LASIK or PRK surgery both use lasers to correct refractive issues.

Additionally, pre-operative testing includes anesthesia preparation. This can include a chest X-ray, electrocardiogram (EKG) , complete blood count (CBC) , and blood chemistry tests . It may also include a test for COVID-19.

The surgery will take place in a hospital or surgical center operating room, or an eye surgery suite.

These ophthalmic surgeries are generally outpatient procedures, meaning you will go home on the same day.

What to Wear

You or your child can wear anything comfortable for the procedure appointment. Eye makeup (or makeup around the eyes) should be avoided, and any hair that can get in or near the eyes should be pinned back and free of styling products.

Food and Drink

Depending on the type of anesthesia used, there will be restrictions in terms of food and drink.

All surgeries done in an operating room under some level of sedation require fluid and food restriction before surgery. Depending on the age of the child, the number of fasting hours may vary. The surgical or anesthesia team will provide specific instructions.

Medications

Typically, blood thinners and anti-inflammatory medications must be stopped for several days before surgery.

Additionally, use of lubricating eye drops or antibiotic ointment may be needed for several days before the surgery. You may also be given a prescription for other medications, such as steroids or a diuretic if there is swelling or inflammation in the brain or eye.

What to Bring

On the day of surgery, you need to bring a form of identification, insurance information, and a method of payment for any portion of the surgery you will be responsible for paying.

If you are having surgery as an adult, someone must be available to drive you home on the day of the procedure.

Children might be allowed to bring a small comfort item to the pre-operative surgical area on the day of surgery.

Pre-Op Lifestyle Changes

Before your surgery, you or your child might be instructed to wear an eye patch on the stronger eye. This can prevent eye muscle weakness or diminished vision from worsening in your weaker eye.  

What to Expect on the Day of Surgery

When you arrive at the surgery appointment, you will need to register and sign a consent form. You will be asked to show identification and insurance information.

If your child is having an eye operation, you may be permitted to go with them to the pre-operative area. Same-day testing may include CBC, electrolyte tests, and a urine test . If an infection is detected, the surgery may need to be rescheduled.

Vital signs, including temperature, blood pressure, pulse, and breathing rate will be monitored. Typically, oxygen saturation will be checked with a pulse oximeter as well.

An intravenous (IV, in a vein) line will be placed in the arm or hand. The ophthalmologist and anesthesiologist may come to do a pre-operative check shortly before surgery.

Then, when it is time for surgery, you will go to the operating room or procedure suite.

Before the Surgery

Preparation includes getting the eye ready for an incision and administering anesthesia.

• With general anesthesia , anesthetic medication is injected through the IV or inhaled through a mask. This medication induces sleep and inhibits pain and muscle movement. A breathing tube is inserted into the throat for mechanical breathing during surgery.
• For IV sedation , anesthetic medication is injected into the IV, inhaled through a mask, or taken by mouth to induce drowsiness. Then local anesthetic medication is injected into the eye with a tiny needle or as eye drops.

Sometimes, an antibiotic ointment is applied to the eye prior to surgery.

During the Surgery

Specific corrective techniques can include:

• PRK surgery: Your ophthalmologist will use eye drops to numb your eyes. They'll remove the outer layer of cells on your cornea using a brush, blade, laser, or alcohol solution. A laser will be used to reshape your cornea.
• Eye muscle surgery: The surgeon makes a small incision in the conjunctiva to access the eye muscles. In a recession procedure, the surgeon reattaches a muscle at a point where it's looser. With a resection procedure, the surgeon shortens the muscle and reattaches it to make it tighter.
• Cataract surgery: In pediatric cataract surgery, a small opening is made in front of the lens capsule. The surgeon inserts an instrument that suctions the inner part of the cloudy lens. An artificial lens is sometimes placed in this surgery or in a second surgery. Dissolvable stitches are used to close the incision.
• Ptosis surgery : The surgeon will make an incision in the crease of the eyelid and shorten the muscle that lifts the lid. In another technique, small incisions are made around the eyebrow and eyelid, and special material is used to connect the eyelid to the eyebrow.

Anesthesia will be stopped or reversed and, if general anesthesia was used, the breathing tube will be removed. The anesthesia team will ensure that you or your child are breathing independently before releasing you to the recovery area.

After the Surgery

While waiting for the anesthesia to wear off, vital signs and oxygen levels will be monitored. Pain medication will be given as needed.

Use of the bathroom without assistance will be permitted. The nurse will ensure that small amounts of food and drink are tolerated.

If no complications occur, then you should be discharged to go home within a few hours after the procedure. You will get instructions about activity restrictions, eye care, who to call if complications arise, and necessary follow-up appointments. A prescription for pain medication and possibly an antibiotic will also be written.

Recovery after ophthalmic surgery and necessary eye care during this time varies and depends on the specific procedure that was done.

Protecting the eye from contamination is important after eye muscle surgery. And you may need to avoid exertion after cataract surgery .

If you are unsure about your recovery period instructions, be sure to call your surgeon's office.

As you are healing from any type of ophthalmic surgery, there are some general considerations to keep in mind.

Keep your eye clean and dry for several weeks after your procedure. Try not to touch your eye and do what you can to prevent dirt, germs, and everyday products (like shampoo) from entering the eye as well.

You might be given a prescription for antibiotics or other medications. Be sure to take them as directed.

You might experience mild pain, discomfort, or swelling for a few days. The pain can usually be managed with over-the-counter pain medication like Tylenol (acetaminophen), and the swelling can be managed with a cold pack.

But if you have more pain or swelling than what you were told to anticipate, you should get in touch with your practitioner's office. Also inform your healthcare provider if any signs of complications arise, including:

• Eye swelling
• Draining pus
• Bleeding from the eye
• Bruising around the eye
• Vision changes

Coping With Recovery

For at least the first week after surgery, you will need to avoid strenuous activities (like heavy lifting) and active motion (like riding a roller coaster) so your eye can heal. Your healthcare provider will give you a timeline for when you can restart these types of activities.

You should be able to read and look at a computer, but give yourself some rest so you don't get exhausted or experience headaches.

Excessive sunlight or bright lights can interfere with healing. You will need to wear sunglasses to protect your eyes from excessive light after you stop wearing a patch.

Sometimes, physical therapy is needed for your eyes. This can include eye movement exercises to strengthen weakened muscles.

Long-Term Care and Vision

Generally, after surgery and recovery are complete, you should experience an improvement in your vision.

That said, you might still have some vision defects after surgery. Your vision might be different than it was before. Your healthcare provider might give you a new prescription for eyeglasses several weeks or months after you heal. You may also need use prescription eye drops to help strengthen your weaker eye. (Children may need to wear a patch.)

After surgery, you will need to have regular eye examinations. If you have a condition that affects your eye health, you might continue to have long-term treatment for that condition.

After any type of eye surgery, dry eyes can be a problem. Using eye drops for lubrication can help prevent this problem.

Possible Future Surgeries

If you have a severe complication, like excessive bleeding or damage to your eye, you could have emergency surgery to alleviate that problem.

And you might need future surgery if you develop another surgically correctable eye problem at a later date.

If your surgery is part of a plan that includes several procedures, you will need to have the next surgery at some point.

Amblyopia happens when one eye doesn't have clear vision, and the brain ignores images from that eye. It's typically treated with non-surgical methods, including wearing a patch over the stronger eye.

Sometimes the cause of amblyopia can be treated with surgery, but only in children. Examples include strabismus, cataracts, refractive errors, and droopy eyelid. However, after surgery, amblyopia will likely need additional treatment to strengthen the connection from the eye to the brain.

A Word From Verywell

Surgical treatment for the causes of amblyopia includes a variety of methods. If you or your child has been diagnosed with amblyopia, surgery isn't likely to be the first therapeutic step. But if surgery is recommended by your ophthalmologist, the outcome can improve your quality of life.

Liu X, Schallhorn SC, Hannan SJ, Teenan D, Schallhorn JM. Three-month outcomes of laser vision correction for myopia and hyperopia in adults with amblyopia .  J Refract Surg . 2020;36(8):511-519. doi:10.3928/1081597X-20200612-02

American Academy of Ophthalmology. Lazy eye surgery facts .

American Academy of Ophthalmology. Amblyopia: What is lazy eye ?

Kraus CL, Culican SM. New advances in amblyopia therapy II:  refractive therapies .  Br J Ophthalmol . 2018;102(12):1611-1614. doi:10.1136/bjophthalmol-2018-312173

National Eye Institute. Amblyopia (lazy eye) .

Doran M. Refractive surgery in children: Narrow indications and improved quality of life . American Academy of Ophthalmology, EyeNet Magazine . November 2013.

Nemours Foundation. KidsHealth. Cataracts .

American Academy of Ophthalmology. Pediatric cataracts .

American Academy of Ophthalmology. What is ptosis?

Centers for Disease Control and Prevention. Common eye disorders and diseases .

American Academy of Opthalmology. Eye screening for children .

Milla M, Piñero DP. Characterization, passive and active treatment in strabismic amblyopia: a narrative review .  Int J Ophthalmol . 2020;13(7):1132-1147. Published 2020 Jul 18. doi:10.18240/ijo.2020.07.18

American Academy of Ophthalmology. Amblyopia: Lazy eye diagnosis and treatment .

Boyd K. What is photorefractive keratectomy (PRK)? American Academy of Ophthalmology.

American Association for Pediatric Ophthalmology and Strabismus. Cataract .

By Troy Bedinghaus, OD Troy L. Bedinghaus, OD, board-certified optometric physician, owns Lakewood Family Eye Care in Florida. He is an active member of the American Optometric Association.

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• Visual problems

Amblyopia (lazy eye)

Peer reviewed by Dr Colin Tidy, MRCGP Last updated by Dr Pippa Vincent, MRCGP Last updated 7 Jun 2023

Meets Patient’s editorial guidelines

Amblyopia (often called a lazy eye) means that vision in one eye does not develop fully during early childhood. Amblyopia is usually a correctable problem if it is treated early. Late treatment can mean that the sight problem remains permanent. A squint (strabismus) is one of the most common causes of amblyopia.

Treatment of amblyopia involves making the lazy eye work harder to see. This is usually done by blocking the vision in the good eye with a patch or by making the eyesight in the good eye blurry by using atropine eye drops.

In this article :

What is amblyopia, understanding the development of vision, what causes amblyopia, how common is amblyopia, how is amblyopia diagnosed and assessed, can amblyopia be corrected, why is treating amblyopia important, what is the outlook for amblyopia.

Continue reading below

Amblyopia is a condition where the vision in an eye is poor because it is not used enough in early childhood and therefore doesn't develop as well. The reason for this underuse is that this eye has poorer vision than the other.

In most cases, only one eye is affected, although it can affect both eyes. Amblyopia is often called a lazy eye. In some cases of amblyopia caused by anisometropia (see below), the problem can sometimes be corrected by glasses. In most cases, however, glasses do not help.

Newborn babies can see but their ability to focus on detail is limited. As they grow, the visual pathways continue to develop from the eye to the brain and within the brain. The brain learns how to interpret the vision signals that come from the eye.

This visual development continues until about age 7-8 years. After this time, the visual pathways and the parts of the brain involved with vision are fully formed and development is finished.

If, for any reason (such as a squint (strabismus) or a cataract ), a young child cannot use one or both eyes normally then vision is not learnt properly by the vision centre in the brain. This results in poor sight (poor visual acuity) called amblyopia. The amblyopia develops in addition to whatever else is affecting the eye.

If the underlying eye problem (eg, squint, cataract) is not treated before the age of about 7 years, the visual impairment from amblyopia usually remains permanent.

Various eye disorders can cause amblyopia. The three most common causes are:

A squint (strabismus) is a condition where the eyes do not look together in the same direction. Whilst one eye looks straight ahead, the other eye turns to point inwards, outwards, upwards or downwards.

This may happen all the time or just when concentrating or when the eye is tired. If the eyes are not straight (aligned), they focus on different things. The result is that the brain ignores the signals from one of the eyes to avoid seeing double.

This means that only one eye is used to focus on objects and the other eye can become 'lazy' (amblyopic), not getting a chance to develop its brain pathways. Most cases of squint occur in early childhood - the critical time when the brain is learning to see.

In some children with squint, the vision in each eye remains normal. In these children, the eye that is used to focus changes from time to time. Consequently, the visual pathways get a chance to develop from both eyes.

However, in most cases of squint, one eye remains the dominant, focusing eye. The other turned (squinting) eye is not used to focus, then fails to develop the normal visual pathways in childhood and amblyopia develops. See the separate leaflet called Squint in Children (Strabismus) for more details .

Refractive errors - particularly anisometropia

Refractive errors are eyesight problems due to poor focusing of light through the lens in the eye. These are the errors that mean people need spectacles for everyday vision. Refractive errors include: short sight ( myopia ), long sight ( hypermetropia ) and astigmatism .

See the separate leaflets called Short Sight (Myopia) , Long Sight (Hypermetropia) and Astigmatism for more details.

If there is a refractive error in one eye, the other eye is usually the same or similar. A situation called anisometropia occurs where there is a difference of refraction between the two eyes. In anisometropia, one eye may be short-sighted (myopic) and the other normal or long-sighted (hypermetropic).

If this difference is large, the brain cannot understand the images coming from both eyes and will choose to ignore the signals coming from one eye. Usually the brain selects the eye with the better refractive error in preference. The other eye (often the most long-sighted one) then becomes 'lazy'.

Refractive errors can usually be corrected with glasses. Prescription lenses change how the lens of the eye focuses light. Unless vision is tested, a parent may not realise their child has a refractive error. This is particularly the case if the child has anisometropia. One eye might have good enough vision to cope well enough and, without anyone realising, amblyopia may develop in the eye not being used.

Other disorders that prevent clear vision

Any disorder in a young child that prevents good vision can lead to amblyopia as the brain fails to develop the visual pathways. This is known as stimulus deprivation amblyopia. For example, a cataract in a lens of an eye or a scarred cornea stops light getting to the back of the eye. This is why it is important to remove a cataract in a child as early as possible. See the separate leaflet called Cataracts for more details .

Even a droopy eyelid can cause amblyopia if it covers enough of the eye to prevent it seeing properly.

About 1 in 25 children develop some degree of amblyopia. Amblyopia is the most common condition treated by children's (paediatric) eye surgeons (ophthalmologists) and professionals who treat eye movement and vision problems (orthoptists).

Amblyopia can be diagnosed by examining the eyes and testing vision. Different techniques are used to test vision depending on the age of the child. Children with a known squint (strabismus) are monitored carefully to see if amblyopia develops.

Children in the UK are usually offered a routine school-entry vision check. One of the main reasons for this is to detect amblyopia whilst it is still treatable. However, even if a child has had an eye check in the past, it is important to see an optician if there is suspicion that vision in one or both eyes has become poor. A very young (pre-school) child can be seen by an optician if there are concerns about their vision.

A baby or child with a suspected amblyopia is usually referred to an orthoptist. Orthoptists are specially trained to assess and manage children with squint and amblyopia. If necessary, an orthoptist will refer a child to an eye surgeon (ophthalmologist) for further assessment and treatment.

Treatments include:

Correcting any underlying eye disorder, such as squint (strabismus), or correcting refractive errors - for example, long sight (hypermetropia) or short sight (myopia).

Training the amblyopic eye to work properly, so that vision can develop correctly.

Correcting the underlying eye disorders

Refractive errors such as short or long sight can be corrected with glasses. Cataracts can be treated with an operation. Improvement in eyesight after being fitted with glasses for a refractive error can take 4-6 months.

Making the affected eye work

The main treatment for amblyopia is to restrict the use of the good eye. This then forces the affected eye to work. If this is done early enough in childhood, the vision will usually improve, often up to a normal level. In effect, the visual development of the affected eye catches up.

Eye patching The most common treatment for amblyopia is eye patching. This entails the good eye being covered with an eye patch, forcing the 'lazy' (amblyopic) eye to see. Eye patches are soft, with sticky edges that fix them to the skin surrounding the eyelids. Eye patching is also called occlusion.

The length of treatment with an eye patch is dependent on the age of the child and the severity of the amblyopia. Treatment is continued until either the vision is normal, or until no further improvement is found. Usually you would be followed up every three months.

If the vision is normal or stable for six months, use of the eye patch may be tailed off. If your child has had cataracts, full-time eye patching may be advised until the age of 7 years. Short breaks would be built into this time, to prevent the good, patched eye from becoming amblyopic due to disuse.

It may take several weeks to several months for eye patching to be successful. On average, patches may be worn for between two and six hours per day. However, in severe cases they may have to be worn for most of the day.

Note : some people wrongly think that eye patching is a treatment to correct the appearance of a squint. Eye patching and other treatments for amblyopia aim to improve vision and do not correct the appearance of a squint.

Further maintenance treatment The child will be followed up, usually until about 8 years of age. This is to make sure that the treated eye is still being used properly and does not become amblyopic again. Sometimes, further patch treatment (maintenance treatment) is needed before the vision pathways in the brain are fixed and cannot be changed.

Other treatments for amblyopia include eye drops. Occasionally, eye drops are used to blur the vision in the good eye instead of an eye patch. Eye drops can be useful when a child refuses to wear a patch.

Once drops are put in a child's eye, the child can't change the blurring of vision; it simply wears off after time. Eye drops may need to be put in each day but sometimes it can be done just at weekends.

Some people find it difficult to hold their child and put drops in the eye but, with practice, it is possible to get used to using eye drops. From a cosmetic viewpoint, using eye drops is less obvious than an eye patch.

The eye drops used to blur the vision usually contain a medicine called atropine . This can occasionally cause side-effects such as eye irritation, reddening (flushing) of the skin, a fast heartbeat ( tachycardia ) and hyperactivity.

Another option is to be fitted with glasses that prevent the good eye from seeing clearly. Usually, one lens of the glasses will be frosted so that it can't be seen through.

Obviously, a young child has to be persuaded to keep the glasses on. One problem with this method is that the child may look around the lens, defeating the object of preventing the eye from seeing.

Rarely, special contact lenses are used for the same job - to blur the vision in the good eye. Contact lenses can be difficult to use in young children. Careful hand washing when handling the lenses is essential to prevent eye infections.

Vision therapy

Vision therapy can be used as a treatment to maintain the good work achieved by eye patching. This involves playing visually demanding games with a child to work the affected eye even harder - like eye training.

A child should do close-up activities when wearing a patch or using other amblyopia treatments. Activities such as drawing and colouring, reading and schoolwork are detailed and work the eye well.

In permanent amblyopia it is impossible to see properly out of one eye. The severity of sight impairment can vary. Although it is possible to function with only one eye, it is always best to have two fully functioning eyes. If there is only good vision in one eye, there is the risk of severe sight problems resulting from an injury or disease of the good eye later in life. So, treatment is usually always advised if it is likely to restore vision.

Even with mild amblyopia, three-dimensional (3D) vision may be affected and it may be hard to have a sense of distance and depth when looking at objects. This can affect eye-hand co-ordination when doing fine tasks like threading a needle or when judging distance for sports like tennis and rounders.

Without a three-dimensional image, people learn to compensate fairly well over time. They are able to judge depth in other ways, such as:

By the position of other objects around.

By shadows.

By the way things move relative to each other in their vision as they move their heads.

A loss of binocular vision (visual input from both eyes) also reduces the size of the visual field, which is the whole area seen at any one time - central and peripheral vision. This is because, when both eyes are functioning normally and looking straight ahead, each sees a slightly different field of vision with the right eye seeing further over to the right and the left eye further over to the left.

When both eyes are working together the brain adds up those two images to produce the whole picture of the world that the brain sees. However, if one eye is being ignored by the brain, the size of the area will be reduced accordingly.

As a rule, the younger the child is treated, the quicker the improvement in vision is likely to be and the better the chance of restoring full normal vision. If treatment is started before the age of about 6-7 years then it is possible to restore normal vision.

If treatment is started in older children then some improvement in vision may still occur. However, full normal vision is unlikely to be achieved. About 1 in 4 children develop a recurrence of amblyopia on stopping treatment.

This risk is higher if patching is stopped abruptly; this is the reason for ongoing monitoring. If the problem returns, further treatment is usually needed. It is very important to follow the advice given by an eye specialist (an orthoptist or ophthalmologist) about patching (or other amblyopia treatments) carefully.

The most common reason for a treatment failure is because the patch has not been worn correctly for long enough. As your child grows older, the vision pathways will become fully formed and impossible to change, so early patching is essential.

It can be difficult to persuade a young child to wear an eye patch. The patch may be annoying and they are likely to try to remove it. Effectively, their sight is temporarily made worse whilst they are wearing the patch. By covering their good eye, they are being forced to use the amblyopic eye. This is often impossible for a young child to understand.

Rewards, such as stickers or star charts, can be used to encourage a child to wear their patch. It is usually easier to patch a baby's eye, as they are less able to remove it. If it is impossible for a child to wear the patch properly, the ophthalmologist or orthoptist may suggest using drops or another method to make the amblyopic eye work.

Hard work in persisting with treatment can give the long-term benefit of good vision so is worth it in the long run.

Dr Mary Lowth is an author or the original author of this leaflet.

Further reading and references

• Guidelines for the Management of Strabismus in Childhood ; Royal College of Ophthalmologists (2012)
• Birch EE ; Amblyopia and binocular vision. Prog Retin Eye Res. 2013 Mar;33:67-84. doi: 10.1016/j.preteyeres.2012.11.001. Epub 2012 Nov 29.
• Lazy Eye (Amblyopia) in Children ; Institute for Quality and Efficiency in Healthcare, June 2020
• Success with Patching ; Oxford University Hospitals

Article History

The information on this page is written and peer reviewed by qualified clinicians.

Next review due: 12 May 2028

7 jun 2023 | latest version.

Last updated by

Dr Pippa Vincent, MRCGP

Peer reviewed by

Feeling unwell?

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A lazy eye (amblyopia) is when the vision in 1 eye does not develop properly. Rarely, both eyes can be affected.

Check if you have a lazy eye

A lazy eye does not always cause symptoms and is often first diagnosed during an eye test.

The main symptoms include:

• shutting 1 eye or squinting when looking at things
• eyes pointing in different directions (a squint )
• not being able to follow an object or person with your eyes
• tilting your head when looking at something
• having tired eyes and rubbing your eyes a lot
• difficulty catching or throwing
• tripping or falling over a lot
• blinking a lot

Many children do not notice anything wrong with their vision.

You can check a younger child's eyes by covering each eye with your hand, 1 at a time. They may complain if you cover their good eye.

Older children may say they're not able to see as well with 1 eye and may have problems with reading, writing and drawing.

Non-urgent advice: Go to an opticians if:

• you're worried about your or your child's vision
• you have not had an eye test for 2 years

What happens during an eye test

To check if you or your child have a lazy eye, an eye test specialist called an optometrist will usually do an eye test.

You'll be asked to look at lights or read letters while different lenses are placed in front of your eyes.

To check the health of your eyes, you or your child may be given eye drops so the optometrist can see the back of your eye more clearly.

If you or your child needs glasses, you'll be given a prescription. You can take this to any optician.

Find out more about eye tests for children

NHS eye tests

NHS eye tests are free for some people, including:

• children aged under 18, or under 19 and in full-time education
• people who have diabetes or glaucoma
• people on some benefits, including Universal Credit

Find out more about free NHS eye tests

Treatments for a lazy eye

How lazy eye is treated depends on what's causing it.

Treatment for a lazy eye aims to improve vision in the weaker eye.

This may include:

• wearing glasses to correct your vision
• wearing an eye patch over the stronger eye for a few hours a day for several months – these are usually worn with glasses
• using eye drops to temporarily blur vision in the stronger eye

Treatment should ideally start before the age of 7, when vision is still developing.

If lazy eye is caused by cataracts or a drooping eyelid, you may need surgery.

You may also need to have surgery if you have a squint. This will straighten the eyes and allow them to work together better, but does not improve your vision.

Some people are entitled to a voucher to help towards the cost of glasses or contact lenses, including:

• if you're on some benefits, including Universal Credit

If you do not have a voucher, you'll have to pay for glasses or contact lenses.

Find out more about NHS optical vouchers

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Page last reviewed: 04 January 2023 Next review due: 04 January 2026

Wandering Eye

by NSG SEO | A Child's Vision , Newsletters | 0 comments

A wandering eye is a type of eye condition known as strabismus or tropia, and it may be caused by damage to the retina or muscles that control the eye, stroke or brain injury, or an uncorrected refractive error like farsightedness. With a wandering eye, one eye deviates or wanders in a different direction when looking at an object.

What Causes a Wandering Eye?

The eyes contain muscles to which they are attached to, and these muscles receive signals from the brain that direct eye movement. Normally, the eyes work together so that they focus in the same direction at the same time. However, with a wandering eye, there is poor eye muscle control and one eye turns away from the object that the person is attempting to hone in on—either up, down, in or out. The eye that turns may do so all the time, or it may only do so at certain times, such as when the person is fatigued, sick or has overworked the eyes as a result of prolonged reading or staring at a computer. There are other cases where the eyes may alternate turning.

Because the eyes are misaligned, the brain receives a different image from each eye. While the brain will learn to ignore the image it gets from the wandering eye, if left untreated, lazy eye or amblyopia can present. This is characterized by a permanent reduction of vision in the traveling eye, and can lead to poor depth perception.

A wandering eye can be classified by the direction the eye turns:

• Inward (esotropia)
• Outward (exotropia)
• Downward (hypotropia)
• Upward (hypertropia)

It may also be classified in other ways:

• Alternating (the eye that turns alternates from left to right)
• Unilateral (always involves the same eye)
• Constant or intermittent (the regularity with which it occurs)

Testing and Treatment

To determine the classification, and in order to develop a treatment plan for a wandering eye, an optometrist will look at a number of factors to understand the cause of the condition, as well as how the eyes move and focus. This may include:

• Looking at the patient’s  family history
• Reviewing the patient’s  medical history
• Observing the external and internal structures  of the turned eye
• Refraction  – a string of lenses are put in front of the patient’s eyes and a handheld instrument with a light source is waved pass. This is done to gauge how the eyes focus and can conclude the lens power needed to correct refractive errors like nearsightedness, astigmatism and farsightedness.
• Visual acuity  – reading letters on distance or near reading charts to measure and estimate the amount of visual impairment
• Focusing and alignment testing   to determine how well your eyes move, focus and work together.

Information gathered from these assessments will help your optometrist devise a treatment plan, which could consist of vision therapy, eyeglasses, prism or eye muscle surgery. If treated early, a wandering eye can be corrected and vision can be restored.

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What causes adult amblyopia and what is the treatment?

I'm 25 years old and have been told I have symptoms of amblyopia in my right eye. I'm confused as I thought it was generally a pediatric disorder. What may have caused this and what is the treatment?

Amblyopia is a general term meaning impaired vision.

Amblyopia ex anopsia is visual loss in children, which, if not treated at an early age, becomes permanent. Children do not complain of it and adults usually are unaware of its presence unless they cover one eye or have an eye test, general physical exam, driver's license exam, etc. The eyes themselves are normal to examination but fail to develop normal vision because they are not stimulated in early childhood. This can occur because of a drooping eyelid , cataract or tumor blocking the entry of light into the eye, a large difference in refractive error (need for eyeglass correction) between the two eyes, or strabismus (failure of the two eyes to align on the same target simultaneously). In the latter case, the brain initially sees double, which is annoying, and learns to suppress one image for comfort. The net result is that the vision loss eventually becomes permanent.

Treatment is directed to the cause and may be surgical removal of the obstruction, correction of the drooping eyelid, cataract surgery , eyeglasses , contact lenses , etc. The earlier the treatment is begun, the faster the correction. Often the child has to wear an eye patch on the GOOD eye, or use eye drops to blur it, forcing use of the eye with the decreased vision. We used to believe that this treatment had to be done by age seven years, but often can work in older children. Pleoptics and flashing light treatments have no proven value. Laser vision correction has been used to correct the refractive errors, but patching is still necessary.

The important message here is that no child is too young to have an eye examination, and parents should consult an ophthalmologist promptly if they notice or suspect anything or if there is a family history of amblyopia. This question was originally answered on Sept. 5, 2012.

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CRISPR therapy restores some vision to people with blindness

The light-absorbing rods and cones in the retina (artificially coloured) deteriorate in people with Leber’s congenital amaurosis. Credit: Science Photo Library

A CRISPR-based gene-editing therapy led to improved vision in people with an inherited condition that causes blindness 1 .

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Thousands Believe Covid Vaccines Harmed Them. Is Anyone Listening?

All vaccines have at least occasional side effects. But people who say they were injured by Covid vaccines believe their cases have been ignored.

Shaun Barcavage, 54, a nurse practitioner in New York City, said that ever since his first Covid shot, standing up has sent his heart racing. Credit... Hannah Yoon for The New York Times

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By Apoorva Mandavilli

Apoorva Mandavilli spent more than a year talking to dozens of experts in vaccine science, policymakers and people who said they had experienced serious side effects after receiving a Covid-19 vaccine.

• Published May 3, 2024 Updated May 4, 2024

Within minutes of getting the Johnson & Johnson Covid-19 vaccine, Michelle Zimmerman felt pain racing from her left arm up to her ear and down to her fingertips. Within days, she was unbearably sensitive to light and struggled to remember simple facts.

She was 37, with a Ph.D. in neuroscience, and until then could ride her bicycle 20 miles, teach a dance class and give a lecture on artificial intelligence, all in the same day. Now, more than three years later, she lives with her parents. Eventually diagnosed with brain damage, she cannot work, drive or even stand for long periods of time.

“When I let myself think about the devastation of what this has done to my life, and how much I’ve lost, sometimes it feels even too hard to comprehend,” said Dr. Zimmerman, who believes her injury is due to a contaminated vaccine batch .

The Covid vaccines, a triumph of science and public health, are estimated to have prevented millions of hospitalizations and deaths . Yet even the best vaccines produce rare but serious side effects . And the Covid vaccines have been given to more than 270 million people in the United States, in nearly 677 million doses .

Dr. Zimmerman’s account is among the more harrowing, but thousands of Americans believe they suffered serious side effects following Covid vaccination. As of April, just over 13,000 vaccine-injury compensation claims have been filed with the federal government — but to little avail. Only 19 percent have been reviewed. Only 47 of those were deemed eligible for compensation, and only 12 have been paid out, at an average of about $3,600 .

Some scientists fear that patients with real injuries are being denied help and believe that more needs to be done to clarify the possible risks.

“At least long Covid has been somewhat recognized,” said Akiko Iwasaki, an immunologist and vaccine expert at Yale University. But people who say they have post-vaccination injuries are “just completely ignored and dismissed and gaslighted,” she added.

In interviews and email exchanges conducted over several months, federal health officials insisted that serious side effects were extremely rare and that their surveillance efforts were more than sufficient to detect patterns of adverse events.

“Hundreds of millions of people in the United States have safely received Covid vaccines under the most intense safety monitoring in U.S. history,” Jeff Nesbit, a spokesman for the Department of Health and Human Services, said in an emailed statement.

But in a recent interview, Dr. Janet Woodcock, a longtime leader of the Food and Drug Administration, who retired in February, said she believed that some recipients had experienced uncommon but “serious” and “life-changing” reactions beyond those described by federal agencies.

“I feel bad for those people,” said Dr. Woodcock, who became the F.D.A.’s acting commissioner in January 2021 as the vaccines were rolling out. “I believe their suffering should be acknowledged, that they have real problems, and they should be taken seriously.”

“I’m disappointed in myself,” she added. “I did a lot of things I feel very good about, but this is one of the few things I feel I just didn’t bring it home.”

Federal officials and independent scientists face a number of challenges in identifying potential vaccine side effects.

The nation’s fragmented health care system complicates detection of very rare side effects, a process that depends on an analysis of huge amounts of data. That’s a difficult task when a patient may be tested for Covid at Walgreens, get vaccinated at CVS, go to a local clinic for minor ailments and seek care at a hospital for serious conditions. Each place may rely on different health record systems.

There is no central repository of vaccine recipients, nor of medical records, and no easy to way to pool these data. Reports to the largest federal database of so-called adverse events can be made by anyone, about anything. It’s not even clear what officials should be looking for.

“I mean, you’re not going to find ‘brain fog’ in the medical record or claims data, and so then you’re not going to find” a signal that it may be linked to vaccination, Dr. Woodcock said. If such a side effect is not acknowledged by federal officials, “it’s because it doesn’t have a good research definition,” she added. “It isn’t, like, malevolence on their part.”

The government’s understaffed compensation fund has paid so little because it officially recognizes few side effects for Covid vaccines. And vaccine supporters, including federal officials, worry that even a whisper of possible side effects feeds into misinformation spread by a vitriolic anti-vaccine movement.

‘I’m Not Real’

Patients who believe they experienced serious side effects say they have received little support or acknowledgment.

Shaun Barcavage, 54, a nurse practitioner in New York City who has worked on clinical trials for H.I.V. and Covid, said that ever since his first Covid shot, merely standing up sent his heart racing — a symptom suggestive of postural orthostatic tachycardia syndrome , a neurological disorder that some studies have linked to both Covid and, much less often, vaccination .

He also experienced stinging pain in his eyes, mouth and genitals, which has abated, and tinnitus, which has not.

“I can’t get the government to help me,” Mr. Barcavage said of his fruitless pleas to federal agencies and elected representatives. “I am told I’m not real. I’m told I’m rare. I’m told I’m coincidence.”

Renee France, 49, a physical therapist in Seattle, developed Bell’s palsy — a form of facial paralysis, usually temporary — and a dramatic rash that neatly bisected her face. Bell’s palsy is a known side effect of other vaccines, and it has been linked to Covid vaccination in some studies.

But Dr. France said doctors were dismissive of any connection to the Covid vaccines. The rash, a bout of shingles, debilitated her for three weeks, so Dr. France reported it to federal databases twice.

“I thought for sure someone would reach out, but no one ever did,” she said.

Similar sentiments were echoed in interviews, conducted over more than a year, with 30 people who said they had been harmed by Covid shots. They described a variety of symptoms following vaccination, some neurological, some autoimmune, some cardiovascular.

All said they had been turned away by physicians, told their symptoms were psychosomatic, or labeled anti-vaccine by family and friends — despite the fact that they supported vaccines.

Even leading experts in vaccine science have run up against disbelief and ambivalence.

Dr. Gregory Poland, 68, editor in chief of the journal Vaccine, said that a loud whooshing sound in his ears had accompanied every moment since his first shot, but that his entreaties to colleagues at the Centers for Disease Control and Prevention to explore the phenomenon, tinnitus, had led nowhere.

He received polite responses to his many emails, but “I just don’t get any sense of movement,” he said.

“If they have done studies, those studies should be published,” Dr. Poland added. In despair that he might “never hear silence again,” he has sought solace in meditation and his religious faith.

Dr. Buddy Creech, 50, who led several Covid vaccine trials at Vanderbilt University, said his tinnitus and racing heart lasted about a week after each shot. “It’s very similar to what I experienced during acute Covid, back in March of 2020,” Dr. Creech said.

Research may ultimately find that most reported side effects are unrelated to the vaccine, he acknowledged. Many can be caused by Covid itself.

“Regardless, when our patients experience a side effect that may or may not be related to the vaccine, we owe it to them to investigate that as completely as we can,” Dr. Creech said.

Federal health officials say they do not believe that the Covid vaccines caused the illnesses described by patients like Mr. Barcavage, Dr. Zimmerman and Dr. France. The vaccines may cause transient reactions, such as swelling, fatigue and fever, according to the C.D.C., but the agency has documented only four serious but rare side effects .

Two are associated with the Johnson & Johnson vaccine, which is no longer available in the United States: Guillain-Barré syndrome , a known side effect of other vaccines , including the flu shot; and a blood-clotting disorder.

The C.D.C. also links mRNA vaccines made by Pfizer-BioNTech and Moderna to heart inflammation, or myocarditis, especially in boys and young men. And the agency warns of anaphylaxis, or severe allergic reaction, which can occur after any vaccination.

Listening for Signals

Agency scientists are monitoring large databases containing medical information on millions of Americans for patterns that might suggest a hitherto unknown side effect of vaccination, said Dr. Demetre Daskalakis, director of the C.D.C.’s National Center for Immunization and Respiratory Diseases.

“We toe the line by reporting the signals that we think are real signals and reporting them as soon as we identify them as signals,” he said. The agency’s systems for monitoring vaccine safety are “pretty close” to ideal, he said.

Those national surveillance efforts include the Vaccine Adverse Event Reporting System (VAERS). It is the largest database, but also the least reliable: Reports of side effects can be submitted by anyone and are not vetted, so they may be subject to bias or manipulation.

The system contains roughly one million reports regarding Covid vaccination, the vast majority for mild events, according to the C.D.C.

Federal researchers also comb through databases that combine electronic health records and insurance claims on tens of millions of Americans. The scientists monitor the data for 23 conditions that may occur following Covid vaccination. Officials remain alert to others that may pop up, Dr. Daskalakis said.

But there are gaps, some experts noted. The Covid shots administered at mass vaccination sites were not recorded in insurance claims databases, for example, and medical records in the United States are not centralized.

“It’s harder to see signals when you have so many people, and things are happening in different parts of the country, and they’re not all collected in the same system,” said Rebecca Chandler, a vaccine safety expert at the Coalition for Epidemic Preparedness Innovations.

An expert panel convened by the National Academies concluded in April that for the vast majority of side effects, there was not enough data to accept or reject a link.

Asked at a recent congressional hearing whether the nation’s vaccine-safety surveillance was sufficient, Dr. Peter Marks, director of the F.D.A.’s Center for Biologics Evaluation and Research, said, “I do believe we could do better.”

In some countries with centralized health care systems, officials have actively sought out reports of serious side effects of Covid vaccines and reached conclusions that U.S. health authorities have not.

In Hong Kong, the government analyzed centralized medical records of patients after vaccination and paid people to come forward with problems. The strategy identified “a lot of mild cases that other countries would not otherwise pick up,” said Ian Wong, a researcher at the University of Hong Kong who led the nation’s vaccine safety efforts.

That included the finding that in rare instances — about seven per million doses — the Pfizer-BioNTech vaccine triggered a bout of shingles serious enough to require hospitalization.

The European Medicines Agency has linked the Pfizer and Moderna vaccines to facial paralysis, tingling sensations and numbness. The E.M.A. also counts tinnitus as a side effect of the Johnson & Johnson vaccine, although the American health agencies do not. There are more than 17,000 reports of tinnitus following Covid vaccination in VAERS.

Are the two linked? It’s not clear. As many as one in four adults has some form of tinnitus. Stress, anxiety, grief and aging can lead to the condition, as can infections like Covid itself and the flu.

There is no test or scan for tinnitus, and scientists cannot easily study it because the inner ear is tiny, delicate and encased in bone, said Dr. Konstantina Stankovic, an otolaryngologist at Stanford University.

Still, an analysis of health records from nearly 2.6 million people in the United States found that about 0.04 percent , or about 1,000, were diagnosed with tinnitus within three weeks of their first mRNA shot. In March, researchers in Australia published a study linking tinnitus and vertigo to the vaccines .

The F.D.A. is monitoring reports of tinnitus, but “at this time, the available evidence does not suggest a causal association with the Covid-19 vaccines,” the agency said in a statement.

Despite surveillance efforts, U.S. officials were not the first to identify a significant Covid vaccine side effect: myocarditis in young people receiving mRNA vaccines. It was Israeli authorities who first raised the alarm in April 2021. Officials in the United States said at the time that they had not seen a link.

On May 22, 2021, news broke that the C.D.C. was investigating a “relatively few” cases of myocarditis. By June 23, the number of myocarditis reports in VAERS had risen to more than 1,200 — a hint that it is important to tell doctors and patients what to look for.

Later analyses showed that the risk for myocarditis and pericarditis, a related condition, is highest after a second dose of an mRNA Covid vaccine in adolescent males aged 12 to 17 years.

In many people, vaccine-related myocarditis is transient. But some patients continue to experience pain, breathlessness and depression, and some show persistent changes on heart scans . The C.D.C. has said there were no confirmed deaths related to myocarditis, but in fact there have been several accounts of deaths reported post-vaccination .

Pervasive Misinformation

The rise of the anti-vaccine movement has made it difficult for scientists, in and out of government, to candidly address potential side effects, some experts said. Much of the narrative on the purported dangers of Covid vaccines is patently false, or at least exaggerated, cooked up by savvy anti-vaccine campaigns.

Questions about Covid vaccine safety are core to Robert F. Kennedy Jr.’s presidential campaign. Citing debunked theories about altered DNA, Florida’s surgeon general has called for a halt to Covid vaccination in the state.

“The sheer nature of misinformation, the scale of misinformation, is staggering, and anything will be twisted to make it seem like it’s not just a devastating side effect but proof of a massive cover-up,” said Dr. Joshua Sharfstein, a vice dean at Johns Hopkins University.

Among the hundreds of millions of Americans who were immunized for Covid, some number would have had heart attacks or strokes anyway. Some women would have miscarried. How to distinguish those caused by the vaccine from those that are coincidences? The only way to resolve the question is intense research .

But the National Institutes of Health is conducting virtually no studies on Covid vaccine safety, several experts noted. William Murphy, a cancer researcher who worked at the N.I.H. for 12 years, has been prodding federal health officials to initiate these studies since 2021.

The officials each responded with “that very tired mantra: ‘But the virus is worse,’” Dr. Murphy recalled. “Yes, the virus is worse, but that doesn’t obviate doing research to make sure that there may be other options.”

A deeper understanding of possible side effects, and who is at risk for them, could have implications for the design of future vaccines, or may indicate that for some young and healthy people, the benefit of Covid shots may no longer outweigh the risks — as some European countries have determined.

Thorough research might also speed assistance to thousands of Americans who say they were injured.

The federal government has long run the National Vaccine Injury Compensation Program , designed to compensate people who suffer injuries after vaccination. Established more than three decades ago, the program sets no limit on the amounts awarded to people found to have been harmed.

But Covid vaccines are not covered by that fund because Congress has not made them subject to the excise tax that pays for it. Some lawmakers have introduced bills to make the change.

Instead, claims regarding Covid vaccines go to the Countermeasures Injury Compensation Program . Intended for public health emergencies, this program has narrow criteria to pay out and sets a limit of $50,000, with stringent standards of proof.

It requires applicants to prove within a year of the injury that it was “the direct result” of getting the Covid vaccine, based on “compelling, reliable, valid, medical, and scientific evidence.”

The program had only four staff members at the beginning of the pandemic, and now has 35 people evaluating claims. Still, it has reviewed only a fraction of the 13,000 claims filed, and has paid out only a dozen.

Dr. Ilka Warshawsky, a 58-year-old pathologist, said she lost all hearing in her right ear after a Covid booster shot. But hearing loss is not a recognized side effect of Covid vaccination.

The compensation program for Covid vaccines sets a high bar for proof, she said, yet offers little information on how to meet it: “These adverse events can be debilitating and life-altering, and so it’s very upsetting that they’re not acknowledged or addressed.”

Dr. Zimmerman, the neuroscientist, submitted her application in October 2021 and provided dozens of supporting medical documents. She received a claim number only in January 2023.

In adjudicating her claim for workers’ compensation, Washington State officials accepted that Covid vaccination caused her injury, but she has yet to get a decision from the federal program.

One of her therapists recently told her she might never be able to live independently again.

“That felt like a devastating blow,” Dr. Zimmerman said. “But I’m trying not to lose hope there will someday be a treatment and a way to cover it.”

Apoorva Mandavilli is a reporter focused on science and global health. She was a part of the team that won the 2021 Pulitzer Prize for Public Service for coverage of the pandemic. More about Apoorva Mandavilli

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Aurora borealis in Tennessee? Northern lights could be visible this weekend. Here's why

Seeing the aurora borealis, or northern lights , is a perennial bucket list for many. But few of us in the southern United States have the opportunity to travel to Alaska or Iceland to witness the spectacular dance of lights across the sky.

That could change for Tennessee residents, as early as Friday night. Thanks to heightened solar activity, the aurora borealis could be coming to the skies above a large portion of the United States this weekend, space weather forecasters said Thursday.

Federal forecasters from  NOAA's Space Weather Prediction Center  said that during previous solar activity of this magnitude, the "aurora has been seen as low as Alabama and northern California."  Experts say  the aurora might be visible Friday, Saturday or Sunday nights.

G4? solar storms? What causes aurora borealis, exactly?

The colorful aurora forms when particles flowing from the sun get caught up in Earth's magnetic field. The particles interact with molecules of atmospheric gases to cause the famed glowing green and reddish colors of the aurora.

The spectacle would be courtesy of a series of coronal mass ejections (CMEs) from the sun, which are forecast to reach the Earth early this weekend and produce the geomagnetic storms that trigger auroras. A G4 (severe) geomagnetic storm watch is in effect for Saturday, May 11, NOAA said. It is the first G4 watch issued since 2005, NOAA added.

The northern lights are the most benign result of solar activity. Strong solar storms – including G4s – can also disrupt some radio communications, harm satellites and even knock out power systems, forecasters warned.

The forecast for the aurora can be fickle

To keep up to date, you can keep an eye on NOAA's short-term forecast that shows the location and intensity of auroras.

What is the weather forecast for Tennessee this weekend?

Your chances of seeing any northern lights activity will be highly dependent on the weather, of course.

"Fingers crossed that we'll get to see this in East Tennessee! Cloud cover forecast for tonight and Saturday night looks good, mostly clear skies are expected," the National Weather Service's Morristown office posted on X Friday .

Weather service forecasters in West Tennessee are predicting mostly clear skies Friday night, with mostly cloudy skies Saturday night. Middle Tennessee , meanwhile, should see mostly clear skies tonight and Saturday night.

Tips for viewing the northern lights

"Go out at night," NOAA said. "And get away from city lights."

The best aurora is usually within an hour or two of midnight (between 10 p.m. and 2 a.m. local time). These hours expand towards evening and morning as the level of geomagnetic activity increases.

There may be aurora in the evening and morning, but it is usually not as active and therefore, not as visually appealing, NOAA said.

Has the aurora borealis been visible in Tennessee before?

According to The Tennessee Conservationist , even though Tennessee typically is not a place where you can view the aurora borealis, the lights will occasionally be visible this year and next year as well.

Northern lights were also seen in 2023 in Tennessee, because the sun is nearing a 2025 peak of a solar discharge cycle, meaning it is releasing a larger number of charged particles into space. The more massive these discharges are, the farther south the lights will be visible.

Liz Kellar is a Tennessee Connect reporter. Email  [email protected] .

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