Eye Muscle Surgery
Strabismus is a general term referring to ocular misalignment due to extraocular muscle imbalance. In short, the eyes are "crooked" or "crossed". Occurring in approximately 2% of children under 3 years of age and about 3% of children and young adults, the condition affects males and females equally. Strabismus has an inherited pattern, i.e., it is much more likely to occur if one or both parents are affected. However, many cases occur without any family history of the disorder.
It is important to recognize strabismus, primarily because, in childhood, it is often associated with the development of amblyopia, or lazy eye. Amblyopia refers to reduced vision, uncorrectable with glasses or contact lenses, due to failure or incomplete development of the visual cortex of the brain.
When an individual's eyes are misaligned, depth perception is substantially reduced. Furthermore, when one eye is deviated in early childhood, the brain may learn to ignore the image from that eye, and amblyopia (lazy eye) often results. It is important to understand that it is usually not just one eye that is deviated but rather that the eyes are misaligned in relation to one another. In essence, both eyes are usually at fault, although one eye may appear to be the "crooked" one. If strabismus develops for the first time in adulthood, the affected individual usually experiences double vision. This occurs because the brain, which no longer has the flexibility of early childhood, is unable to ignore the image from the deviated eye.
The cause of strabismus is usually unknown, however, strabismus is certainly more common in families with a history of the disorder. Several neurological conditions are more commonly associated with strabismus, including Down's syndrome, cerebral palsy, hydrocephalus, and brain tumors. The great majority of children with strabismus, however, have no other associated neurological abnormalities. A cataract, eye tumor, or other eye disorder associated with reduced vision may also be present with strabismus.
Signs and Symptoms of Strabismus
Strabismus is often recognized by casual observers as a "crooked eye". In fact, most cases of strabismus are first noted by a parent or the child's pediatrician prior to examination by an ophthalmologist. All children should have their vision examined between 3 and 4 years of age. The pediatrician's office usually evaluates visual acuity in toddlers; however, the acuity can also by evaluated by a family doctor or an ophthalmologist.
If there is a family history of strabismus, children should have an eye exam by an ophthalmologist at an earlier age, perhaps by twelve to eighteen months of age. In some cases, amblyopia (reduced vision) may occur when there is minimal misalignment of the eyes (microtropia). This type of deviation may be difficult to recognize in a young, uncooperative child, even for the highly experienced pediatric ophthalmologist. This type of deviation becomes important if amblyopia develops, which can only be discovered with evaluation of visual acuity.
Treatment for Strabismus
Treatment of strabismus may include patching of one eye (if amblyopia is present), glasses, or surgery to realign the eyes. Surgery does not resolve amblyopia (poor vision), as this can only be corrected with patching and/or glasses. In some cases, realignment of the eyes occurs with proper prescription eyeglasses; however, many children with strabismus will eventually require surgery to better align the eyes. Surgery involves strengthening or weakening of the eye muscles by disinsertion and reattaching the muscle to a different portion of the eye for improved muscle activity.
In general, once a child develops manifest strabismus (obviously crooked eyes), there is no treatment that will "perfectly" straighten the eyes. The goal of surgery then becomes to realign the eyes as close to normal as possible.