What Is Amblyopia?


Amblyopia, more commonly known as “lazy eye” is a condition in the eye that is characteristic of poor vision. In this condition, the brain does not recognise the vision coming through one eye. Eventually, the vision in the affected eye weakens and the brain only registers the vision through the stronger eye. It is rare that amblyopia affects both eyes.

Contrary to its common name, “lazy eye”, a person with amblyopia cannot control what is happening to their eye. According to the National Eye Institute, amblyopia occurs in 3 out of 100 children and is the most common cause of vision loss in adolescents.1

Early detection and treatment are key to preventing long-term vision problems.

Causes of amblyopia

Amblyopia happens early in life as vision develops. The eyes are competing against one another to send signals to the brain. When one is at a disadvantage, the brain relies more on the stronger eye. Eventually, the brain can ignore all signals from the weaker eye, causing permanent vision loss

Amblyopia has three main causes: deprivation, strabismus, and refractive errors.2 The most severe form of amblyopia is depravation. In this category, causes of this include cataracts, retina damage, and optic nerve damage. Other vision problems left untreated can develop into amblyopia (see risk factors).

Signs and symptoms of amblyopia

Many of the signs and symptoms of amblyopia are similar to other eye conditions. This may be due to the fact that other vision conditions left untreated can develop into amblyopia. 

These symptoms include

  • Poor depth perception, meaning understanding how far something is from them
  • The affected eye “wandering” as if the two eyes are not working together
  • Squinting eyes
  • Shutting one eye
  • Tilting their head

Management and treatment for amblyopia

Once diagnosed, your doctor may prescribe glasses if there are vision problems that can be corrected with lenses. Surgery may be recommended if you have a form of depravation amblyopia such as droopy eyelids or cataracts. 

After treating the other vision problems causing amblyopia, your eye doctor may recommend retraining the brain to recognise vision from the affected eye. Two common treatments include:1

  • Wearing an eyepatch on the unaffected eye. The length of time required for the eyepatch depends on each case of amblyopia
  • Eye drops in the unaffected eye to blur vision so the brain focuses on the affected eye. This may be recommended over the eyepatch if the child pulls off the eyepatch

In adults with amblyopia, treatment to retrain the eyes and reverse vision damage is more difficult than in children. The effects of amblyopia can be reversed if treated early and with continued infrequent treatment to prevent it from coming back.

Diagnosis of amblyopia

The longer amblyopia is left to develop, the more difficult it is to reverse the vision damage. Symptoms may be hard to notice in children, therefore it is important to have regular eye checks during your child’s regular check-ups with their general practitioner (GP). It is important to check your child’s vision at least once before they are 7. Your child’s GP may refer them to an ophthalmologist, also known as an eye doctor, for further testing.

A complete eye exam will be conducted to uncover the underlying causes of the amblyopia. A complete eye exam includes testing:

  • Depth perception
  • Visual clarity, reading differently sized letters from a distance
  • Pupil reflex to light
  • Eye pressure
  • Eye alignment done through a test called “cover-uncover test”
  • Eye motility, such as following your finger as it moves around
  • Peripheral vision tests
  • Dilated eye exam to look at the different components of the eye responsible for vision

Risk factors

It is not well known what exactly causes amblyopia itself but other vision problems can develop into amblyopia. Many of the symptoms of amblyopia can be attributed to some of these other listed eye conditions below. Treating these early can prevent the brain from focusing on the stronger eye.

  • Strabismus
    • Strabismus refers to a condition where the eyes point in different directions such as crossed eyes. This can lead to blurred or double vision. Strabismus can be treated with eye muscle surgery
  • Refractive errors3
    • A refractive error is a very common eye disorder where your eyes cannot focus on objects. You may more commonly know refractive errors by the name of the error. The four most common types are nearsightedness (myopia), farsightedness (hyperopia), astigmatism, and presbyopia. Many of the symptoms of refractive errors align with symptoms of amblyopia. Without treatment with contacts or lenses, the brain may lose connection with the affected eyes
  • Cataract4
    • Cataracts are the cloudiness of your eye, making it hard to see clearly. This condition can affect anyone, but it is commonly seen with age
  • Ptosis
    • Ptosis is a term to describe a droopy eyelid. This can be caused by many factors, including nerve damage or muscle weakness in the eyelid. This blocking of vision can cause the brain to redirect more focus to the unaffected eye


The longer amblyopia is left untreated, the worse the symptoms and the more difficult it is to reverse the damage to the vision. In worst cases, there is complete vision loss in the affected eye. When amblyopia is diagnosed and treated in young children, they have a better chance of retraining their brain to understand signals from both eyes since they are still developing. In adults, it is more difficult to retrain the brain and full vision may not be restored.


Can amblyopia be prevented

In some cases, amblyopia can be prevented if the cause is related to other vision conditions, such as cataracts or refractive errors. If these conditions are treated, it is less likely that amblyopia will develop. However, not all cases are 100% preventable. It is important to catch early to prevent worsening vision or permanent damage to eyesight, so you should take your children for regular eye check-ups.

How common is amblyopia

Amblyopia is one of the most common causes of vision loss in children. It is reported to affect 3 out of 100 children.1 

When should I see a doctor

You should have your child’s vision checked at least once between the ages of 3 and 7. If your child experiences any of the symptoms listed above, make an appointment with your doctor. Early detection and treatment is key to preventing further vision issues.


Amblyopia, more commonly known as “lazy eye”, is a vision condition where the brain cannot register vision from one or both eyes. With time and left untreated, the eye becomes weak and the brain solely focuses on vision from the unaffected eye. This is very common in young children, occurring in 3 out of 100 children. While it is not entirely known what causes one to develop this condition, other vision problems such as blurred vision, cataracts, and droopy eyelids can develop into amblyopia. If diagnosed and treated early, there will be no long-lasting vision defects. Common treatments include covering the unaffected eye for a period of time so the brain can reconnect with the affected eye. Many treatments include treating the risk factors or symptoms of amblyopia. Those with a refractive error, such as nearsightedness, can be treated with prescription lenses or contacts. In more severe cases, such as cataracts, eye surgery can resolve the symptoms.

This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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Sara Nakanishi

Master’s of Science - Genes, Drugs, and Stem Cells - Novel Therapies, Imperial College London

Bachelor of Science - Biochemistry/Chemistry, University of California San Diego

Hello! My name is Sara and I have a diverse background in science, particularly in biochemistry and therapeutics. I am extremely passionate about heart health and mental illness. My goal is to break down complex scientific topics to share with those with non-scientific backgrounds so they can be well-informed about their conditions and ways to live a balanced life. I believe that education and awareness are key to leading a healthy lifestyle and I hope to inspire others through my writing.

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