A: Phyllis, about 2 to 3 percent of children have amblyopia. It's very good that all your preschool children get vision screening to diagnose any problems that are best treated early.

Amblyopia is the loss of vision in one eye that occurs when the vision is unequal between the two eyes. This can occur if the child has strabismus, where one eye drifts outward or inward; if one eye focuses differently because it is more nearsighted, farsighted or has astigmatism, or if there is a cataract blocking the lens in one eye. When there is a difference between the eyes, the child's brain naturally tends to rely on the stronger eye and the weaker eye tends to lose vision.

When amblyopia is diagnosed by 3 years of age and treatment is started early, it's more likely that normal vision can be restored to the weaker eye. If it's not diagnosed and treated by 6, some permanent vision loss is more likely. However, recent studies have found that there is still benefit in treating older children with amblyopia.

In addition to the vision screening done in your preschool, encourage families to talk with their children's doctor about early and periodic eye screening for infants and toddlers. The doctor can do an eye exam with an ophthalmoscope, and a new photoscreening technique can take a photo of a young child's eyes to help check whether they are focusing together. Children 3 and older can usually cooperate with vision screening using the eye charts. If the screening finds any abnormality, the child should have a complete exam with an ophthalmologist as soon as possible.

If an underlying cause of the amblyopia is discovered, it should be treated first. For example, a child who is very nearsighted might need glasses, or a child with a cataract might need surgery. Then, the treatment of amblyopia involves temporarily blocking the vision in the stronger eye to force the child to use and strengthen the weaker eye. This treatment is usually continued for months. The standard treatment has been to have the child wear an eye patch over the stronger eye. However, some children find that the eye patch is irritating or attracts too much attention.

More recently, children have been treated with a daily atropine eye drop or ointment that blurs the vision in the stronger eye. Studies have found that eye patches and eye drops were equally effective in improving vision in 70 to 80 percent of children within six months of treatment. In addition, many children and families found that the eye drops were an easier treatment. Eye exercises may also be prescribed. Sometimes, children with eye muscle problems and misaligned eyes may need eye surgery after the amblyopia treatment.

In preschool, it's important that any child with a disability be treated with sensitivity, be protected from teasing and be allowed to engage in all the activities he's capable of. The more informed the preschool staff, children and families are, the better you can care for children with disabilities.

Get information from the child's parents and doctor about any accommodations you should make in the child's activities. If he's only able to use one eye, his eye may fatigue easily, and he may have decreased spatial awareness and difficulty with hand-eye coordination in catching a ball. You may also consider asking the child's parents if they would like to speak with the staff, children and parents about amblyopia, or whether they might like to invite their child's doctor to come talk about it.