Pediatric Vision Disorders
Amblyopia

Amblyopia—Amblyopia is a medical term which describes poor visual development. A child or an adult with amblyopia has poor visual acuity (clarity or sharpness of vision in one or both eyes). The word comes from the Greek. [ambly- (dull) + -opia (vision)] Amblyopia is often referred to as �lazy eye.� The main causes for amblyopia, or poor visual development, are the following:
(1) Abnormalities in the refractive power (or focus) of the eye.
(2) Misalignment of the eye, or strabismus.
(3) Cloudiness of the normally clear visual pathway, such as from cataract or other abnormalities.

Anisometropia�A Possible Cause of Amblyopia (unequal focus refractive error).
Anisometropia occurs when the refractive error of one eye differs significantly from that of the other eye. If asymmetric refractive errors are present in a young child, one eye sends a clear image to the brain and the other eye sends a blurred image to the brain. The brain pays attention to the clear image, and ignores or �turns off� the signal from the blurry eye, resulting in poor visual development. This is the most difficult type of amblyopia to detect since the eyes may look normal, even though the vision in one eye is significantly worse than the other. The treatment for this type of amblyopia is glasses to correct the anisometropia. Glasses alone do not always improve vision to normal, however. Patching of the better eye is often required in order to stimulate the brain to use the amblyopic or �lazy� eye. Occasionally, glasses alone are all that is required to improve the vision back to normal in this type of amblyopia.

Strabismus�A Possible Cause of Amblyopia
Amblyopia caused by misalignment of the eyes occurs w hen the eyes either cross in, wander out, or misalign in a vertical position. In this instance, the child will see double for a brief period, then the brain will begin to ignore or suppress one of the eyes to avoid double vision. This can lead to a severe from of amblyopia, and may occur in half of the children whose eyes misalign. Some children who have misalignment will maintain good vision in each eye by alternating looking with one eye and then the other. Patching the straight eye will improve the vision in the misaligning eye. However, treatment for the poor vision does not straighten the eyes. This often requires surgery, glasses, or eye exercises. Strabismus is discussed in more detail later in this course.

Cataracts�A Possible Cause of Amblyopia
The cause of the most severe type of amblyopia is cataracts in infants. This is best treated by surgically removing the cataract, correcting the optical focus of the eye, and doing intensive patching at a very early age. This is usually done in the first few months of life, and is continued throughout childhood. Cataracts are discussed in greater detail later in this course.

Treating Amblyopia
The mainstay of treating amblyopia is patching, either full-time during waking hours, or patching the good eye full- or part-time. The younger children are, the shorter the time course required for treatment. Older children, aged six or older, may require months of patching to restore normal levels of vision. Once vision has been restored with therapy, part-time patching or maintenance patching may be required to keep the vision from slipping or deteriorating. Prompt treatment is both a responsibility and an opportunity. Whenever strabismus or amblyopia is suspected, the child should be seen by an eye specialist as soon as possible. Early diagnosis and treatment are the keys to restoration and preservation of good vision in children

How is amblyopia diagnosed?
It is not easy to recognize amblyopia. A child may not be aware of having one strong eye and one weak eye. Unless the child has a misaligned eye or other obvious abnormality, there is often no way for parents to tell that something is wrong. Amblyopia is detected by finding a difference in vision between the two eyes. Since it is difficult to measure vision in young children, the ophthalmologist or optometrist often estimates visual acuity by watching how well a baby follows objects with one eye when the other eye is covered. If one eye is amblyopic and the good eye is covered, the baby may attempt to look around the patch, try to pull it off or cry. Poor vision in one eye does not always mean that a child has amblyopia. Vision can often be improved by prescribing eyeglasses. A comprehensive eye exam will include an examination of the interior of the eye to see if other eye diseases may be causing decreased vision. These diseases include: � Cataracts; � Inflammations; � Tumors; � Other disorders of the inner eye.

Loss of vision is preventable
Success in the treatment of amblyopia also depends upon how severe the amblyopia is and how old the child is when treatment is begun. If the problem is detected and treated early, vision can improve for most children. Sometimes part-time treatment may have to continue until the child is about nine years of age. After this time, amblyopia usually does not return. If amblyopia is first discovered after early childhood, treatment may not be successful. Vision loss from strabismus or unequal refractive errors may be treated successfully at a much older age than the amblyopia caused by cloudiness in tissues in the eye.

When should vision be tested?
It is recommended that all children have their vision checked by their pediatrician, family physician, optometrist, or ophthalmologist at or before their fourth birthday. Most physicians test vision as part of a child�s medical examination. They may refer a child to an eye specialist if there is any sign of an eye condition. New techniques make it possible to test vision in infants and young children. If there is a family history of misaligned eyes, childhood cataracts or a serious eye disease, an ophthalmologist can check vision even earlier than age three.