Lazy Eye | Amblyopia | Symptoms | Treatment

Today I want to talk a bit about the children’s vision problem of a lazy eye. A lazy eye, technically referred to as amblyopia, means that one eye has not developed normally and always has blurred vision, even with the best correction of glasses or contact lenses.


Lazy eye is caused when the brain favours one eye and refuses to use the other because it cannot use the two eyes together. Because the vision is “turned off”, clear vision does not develop in the lazy eye.

How a Lazy Eye Develops

When we are born with normal vision, we learn to use both eyes together within the first few months of life. Our brains take the pictures from the two eyes and “fuse” it into one image. This is called binocularity.

When we have a lazy eye, our brains did not learn to use the two eyes together. At an early age, these children only use one eye, and their brains “turned off” the images coming in from the other eye. This is called suppression. Because the brain suppressed the lazy eye very early in life, normal vision did not have a chance to develop. So the child has lost the ability to see clearly out of that lazy eye, even with the best pair of prescription glasses or contact lenses. The amount of vision lost depends on how early the brain turned the eye off.

Causes of a Lazy Eye


Refractive Amblyopia This is when one eye is more nearsighted or farsighted than the other, making it difficult for the two eyes to focus together. It starts very early in life. An infant has no way of telling his parents that the one eye does not see as well as the other; so his visual system has to handle the problem by itself. Because it’s difficult to fuse the clear image with the blurry one, the brain suppresses the vision in the blurry eye that’s interfering and just uses the clear one. Long term suppression of the blurry eye causes vision to stop developing. Once discovered, treatment involves prescribing glasses, eye patching and vision therapy. This will establish binocularity and assist development of the poor visual skills that did not have a chance to develop on its own.

Strabismic Amblyopia Strabismus, often called crossed eye or squint, is a condition in which the brain is unable to properly align the two eyes. As a result, one eye may point in or out, up or down. When the two eyes are not pointing in the same place, two different images are being sent to the brain. The brain cannot fuse two different images into one and the result is double vision. The brain is then forced to turn off the vision coming from the misaligned eye to avoid seeing double. The child only uses the straight eye to see and vision in the turned eye does not have a chance to develop.

Treatment for a Lazy Eye

To correct amblyopia, the blurry eye must first be forced to work in order to allow the opportunity for clear vision to develop.


The child’s clear eye is covered for 2 to 8 hours a day over la long period of time, from 3 months to a year. By forcing the blurry eye to work, its vision improves.

Patching does have some disadvantages. Because the good eye is covered, the child cannot see well and is often frustrated and uncooperative. It becomes difficult to keep the patch on the child. Also, there is a danger of loss of vision in the clear eye when it is covered most of the time for weeks on end.

The gains form patching is not always permanent. While it improves vision, it does not always improve the vision in the lazy eye to 20/20. And once patching is stopped, the improvement in vision can sometimes reverse itself.


In cases of strabismus (squint/crossed eye), surgery is sometimes recommended. Unfortunately, eye surgery does nothing to restore normal two-eyed vision, a learned process of the brain. Surgery simply makes the eyes appear straight, a cosmetic fix, and not a visual cure. The child will still suppress the lazy eye after surgery.

Vision Therapy

Vision therapy is highly successful in remediating a lazy eye. It not only corrects the poor vision in the lazy eye, but it also corrects the underlying problem of the brains inability to align and use both eyes together, so the gains are permanent. The patient’s brain is trained to stop suppressing the lazy eye and to fuse the images coming from both eyes for normal two eyed vision. This can be done at any age and is prescribed by a developmental/behavioral optometrist.

The “Critical Stage” for Treatment

Some parents are told that a lazy eye can only be corrected when the child is very young, usually age 6 or under. Some optometrists feel that if treatment is not undertaken during this “critical stage” of development, the amblyopia becomes fixed and untreatable. Parents of older children with lazy eyes are often told that it is too late to treat the problem. New research has found that a lazy eye can be corrected at any age when glasses and patching are combined with vision therapy.


A lazy eye is not easily recognized. A child may not even be aware that one of his eyes is not working with the other. If the eye misalignment is so slight, parents will not be able to tell something is wrong just by looking.

It is extremely important for children to develop equal vision in both eyes in order to succeed in school, sports, or any other activity that requires clear vision, good eye hand coordination, and strong depth perception. Children with untreated amblyopia may have a limited choice of career, and if there is an injury to the one good eye, they could be visually impaired or legally blind for life.

For these reasons, it is extremely important for parents to have their child’s eyes examined by an optometrist or ophthalmologist as early as possible so vision problems can be found and treated. Vision can be tested in infants and very young children, and it is recommended that a child be examined at least by the age of three.

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