A lazy eye is when the vision of one of your eyes doesn’t develop the way it should. Doctors also call this amblyopia. Your affected eye doesn’t necessarily look different, although it may “wander” in different directions. That’s where the term “lazy” comes from. The condition will usually only affect one of your eyes, but in certain circumstances, the vision in both of your eyes can be affected.
Without treatment, your brain will learn to ignore the image that comes from the weaker eye. That could cause permanent vision problems. It’s important to note that a lazy eye isn’t the same as a crossed or turned eye. That condition is called strabismus. However, strabismus can lead to amblyopia if your crossed eye gets much less use than your uncrossed one.
If amblyopia goes untreated, temporary or permanent loss of vision can occur. This can include loss of both depth perception and 3-D vision.
• Strabismus amblyopia. It occurs when the eyes are not perfectly aligned. This confuses the brain, which eventually stops paying attention to one of the images and ends up canceling it.
• Amblyopia due to deprivation. This happens when there’s a congenital cataract, a drooping eyelid or “ptosis” or a clouding of the cornea. All these conditions impede the correct visual development.
• Refractive amblyopia. This occurs when there’s a large refractive defect in the eyes. This causes the brain to stop sending messages to the most affected eye. Also, it’s the hardest type of lazy eye to diagnose
Signs of a Lazy Eye
Amblyopia starts in childhood, usually between ages 6 and 9. Identifying and treating it before age 7 brings the best chances of fully correcting the condition.
Common symptoms include:
• Trouble telling how near or far away something is (depth perception)
• An eye that wanders inward or outward
• Eyes that appear not to work together
• Squinting or shutting one eye
• Head tilting
• A tendency to bump into objects on one side
• Poor depth perception
• Double vision
Causes of Lazy Eye
Amblyopia is related to developmental problems in your brain. In this case, the nerve pathways in your brain that process sight don’t function properly. This dysfunction occurs when your eyes don’t receive equal amounts of use. Doctors don’t always know what’s behind some cases of amblyopia. Causes may include:
• Refractive errors. One eye might have much better focus than the other. The other eye could be nearsighted or farsighted. Or it could have astigmatism (distorted or blurry vision). When your brain gets both a blurry image and a clear one, it starts to ignore the blurry one. If this goes on for months or years, vision in the blurry eye will get worse.
• Strabismus. This is when your eyes don’t line up the way they should. One could turn in or out. People who have strabismus can’t focus their eyes together on an image, so they often see double. Your brain will ignore the image from the eye that isn’t aligned. This is an imbalance in the muscles that position the eye that causes the eyes to cross or turn out. The muscle imbalance makes it difficult for both eyes to track objects together
• Cataracts. A cloudy lens inside your eye can make things look blurry. The vision in that eye might not develop the way it should.
Anisometropic amblyopia: A refractive error is when the light is not focused correctly as it travels through the lens of the eye. Refractive errors occur due to nearsightedness, farsightedness or astigmatism in which the surface of the cornea or lens is uneven, causing blurred vision.
• Droopy eyelid (ptosis). A sagging eyelid can block your vision.
• Constant strabismus or turning of one eye
• Genetics or a family history of amblyopia
• Different levels of vision in each of your eyes
• Damage to one of your eyes from trauma
• Drooping of one of your eyelids
Amblyopia usually occurs in only one eye. When it first occurs, parents and children often don’t notice the condition. It’s important to get routine eye exams as an infant and child, even if you show no outward symptoms of eye problems.
Your eye doctor will typically perform a standard eye exam to assess vision in both of your eyes. This involves a series of tests, such as:
• Identifying letters or shapes on a chart
• Following a light with each eye and then both of your eyes
• Having your doctor look at your eyes with a magnifying device
Treatment tends to be more effective the younger the child is. After a child is 8 years old, the likelihood of vision improvement drops significantly but can still be effective.
• Treating an underlying eye problem
• Getting the affected eye to work so that vision can develop
• Cataract surgery or phacoemulsification: If a cataract is the cause of amblyopia, it can be surgically removed under either local or general anesthesia.
• Correcting droopy eyelids: For some people, amblyopia is caused by an eyelid that is blocking the vision to the weaker eye. In this case, the usual treatment is surgery to lift the eyelid.
• Atropine eye drops: These may be used to blur vision in the unaffected eye. Atropine dilates the pupil, resulting in blurring when looking at things close up. This makes the lazy eye work more. Atropine is usually less conspicuous and awkward for the child, compared with a patch, and can be just as effective.
• Vision exercises: This involves different exercises and games aimed at improving vision development in the child’s affected eye. Experts say this is helpful for older children. Vision exercises may be done in combination with other treatments.
Lazy Eye Risk Factors
A child might be more likely to have a lazy eye if they:
• Were born early (premature)
• Were smaller than average at birth
• Have a family history of amblyopia or other eye conditions
• Have developmental disabilities.
• Blindness: If untreated, the patient may eventually lose vision in the affected eye. This vision loss is usually permanent. According to the National Eye Institute, lazy eye is the most common cause of single-eye vision impairment in young and middle-aged adults in the U.S.
• Eye turn: Strabismus, where the eyes are not properly aligned, can become permanent.
• Central vision: If amblyopia is not treated during childhood, the patient’s central vision may not develop correctly. The problem may affect their ability to do certain tasks.
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