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Treatment options for amblyopia

In the past, eye doctors have recommended patching the good eye with a self-stick patch that completely blocks vision in order to stimulate the weaker eye. The number of hours the child is told to wear the patch can vary—from a few hours to all waking hours each day. But as you can imagine, children often resist wearing the patch because they can't see as well and the skin can become irritated from the patch.

They may be embarrassed to wear it to school and all too often, don't. Past studies have shown that as many as half of the children won't wear it. The best compliance rate has been 87 percent. As a result, children do not gain the benefit of this type of therapy.

Because of these low compliance rates, doctors have been searching for more acceptable alternatives. The idea of an alternative to patching in children age three to seven is very powerful. This study suggests that drops are a good alternative. It's much easier on both the parents who have to give the treatment and the children who live with it.

What goes wrong
Amblyopia is a condition in which a child has a weaker eye from abnormal visual development. There are three major causes of amblyopia: strabismus, unequal focus and cloudiness in normally clear ocular tissue.

Strabismus
In strabismus, a misalignment of the eyes, the eyes appear crossed or one eye is turned out. If both eyes were working normally, the child would see double, so over time the brain turns off the vision in one eye and amblyopia results.

Unequal focus
Refractive errors are eye conditions such as near sightedness, far sightedness, or astigmatism, which are corrected by focusing an object with glasses. When what is seen by one eye is blurred due to not wearing glasses, the blurred eye may stop developing and become amblyopic.

Cloudiness
Another cause is a structural block, such as a cataract, a clouding of the naturally clear lens in the eye. A cataract prevents a clear image from being seen by the eye and can lead to amblyopia.

Signs to watch for in amblyopia:

• If a child's eyes are not aligned or straight when you look at them
• If one eye wanders out or crosses in from time to time independent of the other eye
• If there is a family history of amblyopia

Correction of amblyopia
There is a window during development in which to fix these problems—most notably before age eight. After eight, it is harder to restore vision in the amblyopic eye. Treatment of the good eye with either the patch or drops forces the weaker eye to work harder. The drops work by relaxing the good eye so it cannot focus properly up close. The pupils of the eye are dilated by the drops so protective sunglasses are recommended when outdoors.

If a child does not have an eye that is misaligned, it can be difficult to detect amblyopia since a child can appear to have normal vision with both eyes open. All children should have their eyes checked at age four either by their pediatrician, family practitioner or ophthalmologist, a medical doctor who specializes in treating eyes.

Amblyopia runs in families so if a family member has amblyopia, all young relatives should be checked. A difference in vision between the two eyes can raise the question of amblyopia. Sometimes only glasses are needed, but if the vision is not corrected with glasses alone, amblyopia treatment is necessary.

It's important to note that drops are best for children with mild to moderate amblyopia, in the range of 20/40 to 20/100 visual acuity. For children who have vision worse than 20/100, doctors will advocate patching. Atropine drops are not as effective in these cases.

The key to this treatment is compliance and in looking at the questionnaire the parents in the study had to fill out, it was clear the drops were easier to use. This study will continue for two more years so I'll be watching for those results in the future. In the meantime, it will definitely change the way I practice, although there are some children who will hate the drops and prefer the patch.

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Dr. Howard is an attending physician in pediatric ophthalmology at Yale-New Haven Children's Hospital.