Amblyopia is the name for diminished vision in one or both eyes, usually without any obvious defect. Amblyopia is not the same as nearsightedness, farsightedness, or astigmatism, which can be corrected with eyeglasses or contact lenses.
There are two main types of amblyopia: "lazy eye" amblyopia, and toxic amblyopia.
Lazy eye amblyopia occurs frequently in young children whose eyes do not line up correctly - a condition known as strabismus. To prevent double vision (in which the patient sees two images of everything), the brain suppresses the sight of one eye so that the other eye does all the work. The brain structures dependent on the eye that is not working may atrophy (waste away) or fail to develop. There are usually no obvious symptoms. By the time the condition is recognized, vision may be permanently damaged.
Usually, the child appears to see as well as the next child. Sometimes, however, the condition that causes the amblyopia is very noticeable: the eyes may turn either inward or outward, or one eye may be looking up while the other is looking down.
Strabismus affects approximately 4 percent of U.S. children under the age of 6. Amblyopia occurs in about 2 percent of the general population. Strabismus can occur as crossed eyes. In others, it may manifest as eyes that turn out, up or down. Its name can be traced to the Greek word strabismos - to look obliquely or with un-straight eyes. Some use the terms "squint" and "lazy eye."
Strabismus can disable sight in one eye, yet leave the other with 20/20 vision. Strabismus can be acquired from diverse causes at any age.
Prompt attention to correcting eye misalignment will provide the most satisfactory outcome of treatment. Indeed, if some cases of strabismus are left untreated until age 6, permanent visual impairment can result.
Treatment has three primary goals: foremost, to obtain the best possible vision in each eye; second, to gain the best possible alignment of each eye alone and as a pair; and, finally, to provide the best possible opportunity for binocular vision. Corrective eyeglasses, patching, or both are the mainstay therapies, with about 30 percent of patients needing surgery.
Corrective eyeglasses can help children as young as 6 months of age. They are most effective when there is significant farsightedness and the eyes turn in. They may be the only therapy needed in about a third of these patients whose eyes turn in. Prisms incorporated in eyeglasses may relieve double vision in some older patients.
To force use of a "lazy" eye while preserving vision in the preferred eye, patching can be very effective. If a child does not develop vision equally in each eye early in life, it may never develop fully. For a 4-month old child, patching might be used only an hour or two each day. A child that age probably takes 2 or 3 naps a day, so patching may be used for one of those waking periods. If the eye is covered for too long a period at this time, the child can lose sight in that eye and the loss could be irreversible.
Should a specialist be consulted?
Do any tests need to be done to rule out any other eye problem?
Has any permanent damage already occurred?
What has caused this condition?
What treatment do you recommend?
How successful is it?
How long will the treatment need to be continued?
Will surgery be needed to correct the problem? What is the procedure?
What can be expected after the surgery?
Early vision screening may help identify patients at a stage where patching is sufficient therapy. Newer devices are being developed to measure vision in infants using electrode stickers placed on the child's scalp.