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Lazy eye (amblyopia)

Published by Bupa's Health Information Team, September 2011.

This factsheet is for parents of children who have a lazy eye, or who would like information about it.

A lazy eye happens when poor vision in one eye leads to the brain ignoring the visual signals from that eye and instead only using the ‘good’ eye to see. This condition most commonly affects only the vision from one eye, but can sometimes affect both.

The term ‘lazy eye’ is commonly used in place of ‘amblyopia’ so this will be used in this factsheet. A lazy eye can be confused with a squint (where the eyes are not aligned) or a drooping eyelid (ptosis) but these are different conditions.

About lazy eye

A lazy eye is when the eye and the brain aren’t working together properly so that the vision in one of the eyes is poor. The affected eye usually looks fine physically, but it isn’t being used as much because the brain is favouring the other eye. The eye that isn’t being used properly may be called a ‘lazy eye’. It's thought that up to three in 100 children have a lazy eye.

A lazy eye usually begins in childhood, during a key phase when your child's vision is still developing and his or her brain is learning to understand the information coming from the eyes. This process is usually complete by age eight. A lazy eye is a problem with the development of vision by your child's brain rather than a disease or condition affecting the eye itself.

When your child looks at an object, each eye picks up an image. This information is sent to the brain and turned into one image. The images from each eye provide slightly different information about the object, which enables your child to judge depth (the ability to determine the distance between objects).

If your child has a problem with the images from one eye, for example if the visual image from one eye is somehow too different to that from the other, because the eyes aren't both facing the same direction or the image is blurred, then a lazy eye could develop. When this happens, the brain starts to ignore the poor image and uses just the image from the other eye.

If your child’s brain only takes in the visual information from one eye, he or she will have a reduced ability to judge depth. This may not be an immediate concern but it could mean your child has problems reading, doing some sports and, in later life, may make certain careers impossible, for example becoming a pilot. Also, relying on vision in one eye alone could lead to serious sight problems if vision in the other eye is affected later in life.

Symptoms of lazy eye

Often, your child will have no obvious symptoms of having a lazy eye and won’t know that one eye is working better than the other. Even if your child does notice a difference, he or she may not be able to explain that his or her vision differs in each eye. If your child is young, it may be easier to notice that he or she has a lazy eye by covering one eye at a time. It’s likely that when the eye that is working well is covered your child will try to push the cover away. If your child is older, he or she may mention having problems seeing with one eye.

For some children who have a lazy eye, you may be able to notice that their eyes look different to each other. One eye may look in a different direction to the other (a squint), one eye may be cloudy (from a cataract for example) or one eyelid may be drooping and covering part of that eye (a ptosis). These physical eye problems could cause a lazy eye to develop and will need to be treated before your child can be treated for a lazy eye.

These symptoms aren’t always caused by a lazy eye, but if your child has them, see your GP.

Complications of lazy eye

If a problem with the vision in one eye is left untreated, it can lead to a permanent loss of vision in that eye. A squint can also develop and your child’s ability to judge depth may be affected (this may lead to your child being unable to do certain occupations later in life). However, lazy eye does not cause complete blindness and your child will still be able to get around obstacles when using his or her affected eye. Occasionally the development of vision in both eyes will be affected.

Vision development continues until about age eight – after this it is much more difficult to treat a lazy eye and correct your child’s vision.

Underlying causes of a lazy eye may occasionally lead to more serious health problems. Therefore, if you think your child may have a lazy eye, it’s important to see your GP.

Causes of lazy eye

The visual information from one of your child's eyes may be ignored by the brain as a result of the following eye conditions.

  • A squint – when the muscles that control eye movement are out of balance. This means that one eye looks forward at the object in focus, whereas the other eye turns away (usually either outwards or inwards).
  • Anisometropia – when there is unequal vision in each eye as a result of refractive errors. This is when one eye is able to focus on an object but the other eye can't, and can be caused by long-sightedness, short-sightedness or astigmatism (where the cornea at the front of the eye isn’t perfectly curved).
  • Isoametropia – when there is a high level of equal long-sightedness or short-sightedness in both eyes (usually long-sightedness) resulting in an unfocused image at the back of the eye.
  • Ptosis – a condition affecting the muscles in the eyelid causing it to droop down. The drooping eyelid blocks some of the vision in that eye, whereas the other eye has full vision.
  • A cataract – a clouding in the lens of the eye. If your child is born with a cataract it's called a congenital cataract.
  • An injury affecting vision in one eye only can lead to the development of a lazy eye.
  • Your child may be born with problems affecting the part of the eye that is sensitive to light (the retina) or the nerve that transmits signals from the retina to the brain (optic nerve).

Diagnosis of lazy eye

If your GP thinks your child may have problems with his or her vision, he or she will refer your child to an orthoptist or an ophthalmologist. An orthoptist is a health professional who specialises in eye movement problems such as squints, lazy eyes and double vision. An ophthalmologist is a doctor who specialises in eye health, including eye surgery.

An orthoptist will carry out routine assessments using specialised techniques to determine whether your child is at the right stage of visual development. Often orthoptists do screening before children start school to identify those who might otherwise go untreated.

An ophthalmologist will carry out a detailed examination of your child's eyes to exclude any other causes of poor vision. If the ophthalmologist thinks that your child has a lazy eye or is at high risk of developing one, it may be necessary to monitor your child for several years.

Even if your child has previously had an eyesight check, it's still worth seeking advice if you have any concerns about his or her vision.

Treatment for lazy eye

It's important to get treatment for your child's visual problems as early as possible. After about the age of eight, treatment may not be effective.

The success of treatment for your child's lazy eye will depend on what is causing it, his or her age, level of vision at diagnosis and how carefully your child sticks to the treatment plan.

Your child may only need to wear a pair of glasses (or sometimes contact lenses). These will correct the blurring caused by long- or short-sightedness in the affected eye, or help to stop your child's eyes from squinting. It's important to try to ensure that your child wears his or her glasses as instructed by your orthoptist or ophthalmologist and to report back any problems.

More involved treatment aims to force the affected (lazy) eye to start working again. This is done by covering or blurring the vision in your child's other eye using either a patch (occlusion) or, less frequently, eye drops and ointments (penalisation). Occasionally, your child may be prescribed glasses or contact lenses to blur the vision in his or her other eye.

Your child may need to wear the eye patch for several hours a day over many weeks or months, or use eye drops or ointments for several days at a time.

There is a risk that the other eye may become lazy if it’s covered up too much or for too long. Your orthoptist or ophthalmologist will monitor your child's progress carefully and adjust treatment accordingly, but it's important to follow his or her advice and instructions, and to report back any concerns. Getting your child to wear a patch over his or her better eye can be hard work. If the treatment proves too difficult, talk to your orthoptist or ophthalmologist about other options.

Any conditions found to be causing your child's visual problems will also be treated or monitored by your ophthalmologist.

 

For answers to frequently asked questions on this topic, see FAQs.

For sources and links to further information, see Resources.

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  • This information was published by Bupa's Health Information Team and is based on reputable sources of medical evidence. It has been reviewed by appropriate medical or clinical professionals. Photos are only for illustrative purposes and do not reflect every presentation of a condition. The content is intended only for general information and does not replace the need for personal advice from a qualified health professional. For more details on how we produce our content and its sources, visit the about our health information page.

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  • Publication date: September 2011