Strabismus, commonly called lazy eye or squint, is a condition in which the eyes are not looking in the same direction.
Squint (strabismus) typically involves a lack of coordination between the extraocular muscles that prevents bringing the gaze of each eye to the same point in space and preventing proper binocular vision, which may adversely affect depth perception. Strabismus can be either a disorder of the brain coordinating the eyes or a disorder of one or more muscles, as in any process that causes a dysfunction of the usual direction and power of the muscle or muscles.
Diagnosis
During eye examinations, ophthalmologists, orthoptists, and optometrists typically use a cover test to aid in the diagnosis of strabismus. If the eye being tested is the strabismic eye, then it will fixate on the object after the "good" eye is covered, as long as the vision in this eye is good enough. If it is the "good" eye, there will be no change in fixation, as it is already fixated. Depending on the direction that the strabismic eye deviates, the type of tropia or phoria may be assessed.
A simple screening test for strabismus is the Hirschberg test. A flashlight is shone in the patient's eye. When the patient is looking at the light, a reflection can be seen on the front surface of the pupil. If the eyes are properly aligned with one another, the reflection will be in the same spot of each eye. Therefore, if strabismus is present, the reflection from the light will not be in the same spot of each eye.
Treatment and management
As with other binocular vision disorders, the primary therapeutic goal for those with strabismus is comfortable, single, clear, normal binocular vision at all distances and directions of gaze.
Whereas amblyopia, if minor and detected early, can often be corrected with use of an eyepatch on the dominant eye and/or vision therapy, the use of eyepatches is unlikely to change the angle of strabismus. Advanced strabismus is usually treated with a combination of eyeglasses or prisms, vision therapy, and surgery, depending on the underlying reason for the misalignment. Surgery attempts to align the eyes by shortening, lengthening, or changing the position of one or more of the extraocular eye muscles and is frequently the only way to achieve cosmetic improvement. Glasses affect the position by changing the person's reaction to focusing. Prisms change the way light, and therefore images, strike the eye, simulating a change in the eye position.
Early treatment of strabismus and/or amblyopia in infancy can reduce the chance of developing amblyopia and depth perception problems. Eyes that remain misaligned can still develop visual problems. Although not a cure for strabismus, prism lenses can also be used to provide some comfort for sufferers and to prevent double vision from occurring.
In adults with previously normal alignment, the onset of strabismus usually results in double vision (diplopia).
Although the mainstream medical community regards the Bates method with skepticism, advocates assert that it can reverse strabismus.
Prognosis
When strabismus is congenital or develops in infancy, it can cause amblyopia, in which the brain ignores input from the deviated eye. Both strabismus and amblyopia are sometimes referred to as lazy eye. The appearance of strabismus may also be a cosmetic problem. One study reported that 85% of adult strabismus patients "reported that they had problems with work, school and sports because of their strabismus." The same study also reported that 70% said strabismus "had a negative effect on their self-image."
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