Impaired vision in an eye that is usually structurally normal
Amblyopia develops in young children if each of the two eyes send a different image to the brain. The development of vision occurs until a child is about 5 years old and depends on the brain learning to combine the images from both eyes. If each eye produces a different image during this period, the brain responds by suppressing images it receives from the more unfocused eye, and vision does not develop normally. If the underlying cause is not treated by the age of 10, later attempts to correct vision will fail.
Any condition that causes each eye to send a different image to the brain may lead to amblyopia. Misalignment of the gaze of the eyes (see Strabismus) is the most common cause of amblyopia. Other causes include vision disorders in one eye, such as astigmatism, shortsightedness (see Myopia), and longsightedness (see Hypermetropia). The condition sometimes runs in families, suggesting that genetic factors are involved.
If you suspect that your child cannot see clearly, you should consult the doctor without delay to minimize the risk of permanent visual impairment. Your child will probably be referred to an ophthalmologist, who will examine your child’s eyes and assess vision (see Vision tests in children).
Treatment depends on the underlying cause of amblyopia. If your child has a vision disorder such as shortsightedness, this may be corrected by wearing glasses. If vision in one eye is reduced, wearing a patch over the good eye for at least 5 hours each day for several months forces the brain to process visual information from the weaker eye, whatever the underlying cause. If your child has to wear an eye patch to correct amblyopia, he or she will need support and encouragement, especially if vision in the affected eye is poor.
Left untreated, strabismus may lead to amblyopia. In some cases, an operation to correct strabismus is necessary to prevent amblyopia from developing.
The outlook for children with amblyopia depends on when the condition is detected and treatment to correct it begins. Amblyopia is usually at least partially reversible in children under the age of 10. Older children with the condition will probably already have some degree of permanent visual impairment.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.