Wed, 03 Sep 2003

Amblyopia can lead to functional blindness

Donya Betancourt, Pediatrician,

Amblyopia is the most common cause of monocular visual (vision) impairment in children and young and middle-aged adults.

Amblyopia usually begins in infancy or childhood. Amblyopia, also known as "lazy eye", has many causes. Most often it results from either a misalignment of a child's eyes, such as crossed eyes (strabismus), or a difference in image quality between the two eyes (one eye focusing better than the other.)

In both cases, one eye becomes stronger, and causes the brain to shut down the messages from the weak eye, which will eventually lead to functional blindness in that eye.

All babies are born with poor eyesight. As babies grow, their eyesight gets better. Good eyesight needs a clear, focused image that is the same in both eyes. If the image isn't clear in one eye, or if the image is not the same in both eyes, the vision pathways will not develop correctly.

In fact, the pathways may actually get worse. Because there are several causes of amblyopia, the treatment must match the problem. Glasses fix some problems. Surgery may be needed for cataracts, droopy eyelids or crossed eyes. After the cause of the amblyopia is found, the child will need to use the weaker eye most of the time, so it will get stronger.

The vision pathways in the brain must become strong early, when children are very young. The first few years of life are the most important for eyesight. After a child is 8 to 10, the brain's vision system is complete. It cannot develop anymore. If the amblyopia has not been treated by this age, the child will have poor vision for life. It will not be possible to fix it with glasses, patching or any other treatment.

To make the child use the weaker eye, a patch can be put over the stronger eye. Sometimes, eye drops or special glasses are used to blur the vision in the stronger eye. This makes the weaker eye become stronger. The treatment usually lasts until vision is normal, or until vision stops getting better.

For most children, this takes several weeks. A few children need to use eye patches until they are 8 to 10 years old. There's a small chance that using an eye patch for too long can hurt the strong eye. For this reason, children who are wearing eye patches should see their doctor often during the treatment.

For decades, patching the unaffected eye has been the mainstay of amblyopia treatment. Compliance has been compromised, according to the investigators, because many children with amblyopia have been required to wear an eye patch during school hours. For these children, the accompanying social and psychological stigma is real.

There was a study published in the May issue of the Archives of Ophthalmology the outcome of two hours of eye-patching daily combined with one hour of near visual activities daily was as good as six hours of patching per day.

Because the daily burden to administer treatment for amblyopia falls on the parent, the findings from this study will immediately affect families that have young children with this eye disorder, study chairman Michael Repka MD, in Baltimore, Maryland, says in a news release.

The findings make it much easier for parents to monitor their children and encourage children to successfully comply with treatment. Timely and successful treatment for amblyopia in childhood can prevent lifelong visual impairment.

Since amblyopia usually occurs in one eye only, many children may be unaware of the condition. As many parents do not take their infants and toddlers in for an early comprehensive vision examination, many children go undiagnosed until they have their eyes examined at the eye doctor's office at a later age.

Age nine is the upper limit for any hope of vision recovery. If there is any way for you to have your child screened by an eye doctor, please do so. School screenings are not reliable. The most important diagnostic tools are the special visual acuity tests other than the standard letter charts used by the eye doctor. Examination with cycloplegic drops is necessary to detect this condition in the young.

It should be remembered, the earlier that amblyopia is detected the better the chances for vision recovery. If not treated early enough, an amblyopic eye may never develop good vision and may even become functionally blind.