Amblyopia

Amblyopia is a condition in which one eye has reduced or dim vision but is otherwise healthy. Amblyopia is the most common cause of childhood visual impairment, affecting 2-3% of all children. Although this impairment is treatable, it must be addressed as early as possible to achieve the best outcome.

For vision to develop fully, the brain and the eyes must work together. Images are presented to the eyes and transferred to the brain, stimulating the continued development of vision. However, should one eye receive inadequate visual input, the visual pathway will not develop appropriately, leaving the vision of that eye impaired.

There are a number of causes of reduced visual input to an eye. Children who have strabismns, or misaligned eyes, may develop amblyopia. If the eyes are not aligned, the stronger eye may be the only eye that functions sufficiently for continued effective vision development. The eye that is weaker or used less frequently may develop visual impairment. Also, if the visual acuity in one eye is much worse than in the other eye, the stronger eye will receive adequate input, while the eye with decreased acuity may be prone to disuse and amblyopia. Other causes involve any condition that blocks the eye from receiving visual stimulation. This may occur if there is a cataract or a droopy eyelid.

There are no clear-cut signs of amblyopia. Children are usually not aware of a problem, and are therefore unlikely to complain. However, a parent might notice that a child demonstrates certain compensatory actions. While trying to read, a child might close one eye or squint. In order to see objects, the child may turn the head preferentially to one side or hold the head at an awkward angle. Of course, if the child has strabismus or some other discernable abnormality that may obscure vision, the child is at risk for amblyopia.

Since amblyopia is treatable, especially in younger children, every effort should be made for a timely diagnosis of this disorder. Vision screening is very important. Commonly, this is performed during routine medical exams. Schools also offer visual screening. Traditional vision screening requires that the child be able to participate in the testing process. The child needs to be able to cooperate and communicate for the testing to be useful. Diagnosing amblyopia early is important, and researchers are attempting to validate other forms of vision testing for children who cannot effectively undertake traditional vision testing. One such method is photoscreening. A special camera takes a picture of the eye to look for visual abnormalities. Although this screening method is still being developed, it has the potential to offer screening to infants, non-verbal children or children with developmental delays.

Early treatment of amblyopia has been the mainstay of ophthalmologists. Treatment for amblyopia was believed effective only until the child was perhaps eight or nine years old. Recent evidence has documented visual improvement in children with amblyopia up to the age of 18, however. More studies are under way to determine if these improvements in older children are maintained once the treatment has been completed. Certainly, the earlier the problem is treated, the better the prognosis, but older children can also achieve good results with appropriate treatment.

Once amblyopia has been diagnosed, the child should be seen by a pediatric ophthalmologist for treatment. The goal of any therapy is to optimize and, if possible, normalize the visual acuity in the weaker eye. Available treatments depend on the cause of amblyopia. For eyes with a visual discrepancy that can be corrected by glasses, a trial of glasses should be pursued. For children with a discrepancy that cannot be corrected or who do not respond to a trial of glasses, two different forms of therapy are available.

One form of treatment is for the child to wear an eye patch over the stronger eye to induce the weaker eye to do the work. In the past, patches were worn for prolonged periods. However, research suggests that less patch time is just as effective. For moderate amblyopia, 2 hours of patching with 1 hour of near work is just as effective as 6 hours. In those with severe problems. 6 hours is sufficient, instead of 12 hours. This discovery has been very important in the management of amblyopia treated by patching.

Children do not relish the idea of wearing a patch, particularly in social settings like school. However, since the time needed to wear the patch has been shown to be much shorter, compliance has increased. Additionally, the burden on the parent has been somewhat relieved. Often the parent needs to monitor that the child is indeed wearing the patch. This is more easily accomplished when the patch is needed for less time.

Another treatment nearly as effective as patching in treating amblyopia is the use of atropine eye drops to blur the vision in the strong eye. This also forces the weaker eye to do the work. Since both methods appear to work effectively, the treatment can be tailored to the needs of the family and the child. If a child is likely to be non-compliant with an eye patch, atropine can be chosen. On the other hand, some children cannot tolerate the use of eye drops; clearly a patch would be more suitable.

Whichever treatment is chosen, compliance with that therapy is essential, along with regular follow-up evaluations with the ophthalmologist. The specified treatment needs to be followed in order for the child to benefit. This may require some persuasion and support by the family, but the result is worth the effort. There are different resources available for people affected by amblyopia. Patches with different logos and designs can be purchased. In addition, there is a club called the Eye Patch Club that children with amblyopia can join. The club offers education for children, families and schools. Those children who are interested can become pen pals with others that are also being treated for amblyopia.

Amblyopia can be treated quite effectively. To reduce the occurrence of this common visual impairment, several undertakings need to be pursued. To begin with, physicians need to be aware of the diagnosis, and that intervention may be beneficial through adolescence. Additionally, continued research on effective screening methods needs to continue in order to reach as many individuals as possible. Finally, appropriate therapy should be available to those who suffer from amblyopia. The treatment can lead to visual improvement and is relatively inexpensive. Efficacious treatment of amblyopia will go a long way in improving the visual health of the world.

Marilyn Moss is a retired physician living in Connecticut. After retiring from Yale University, she began to pursue an interest in writing about health-related issues. She has had other articles in Pediatrics for Parents.

COPYRIGHT 2005 Pediatrics for Parents, Inc.
COPYRIGHT 2006 Gale Group