Strabismus, more commonly known as crossed-eyes, is a vision condition which a person is unable to align both eyes simultaneously under normal conditions. One or both of the eyes may turn in, out, up or down. The fovea of each eye is used for precise vision. When they do not point at an object at the same time, the result is an appearance that the eyes are “turning” in relation to each other. This turning in may be constant, when the eye turns all of the time or may be intermittent, turning only under stressful situations or when ill. It is estimated that up to 5 percent of all children have some type or degree of strabismus. Children with strabismus may initially have double vision. This occurs because of the misalignment. In an attempt to avoid double vision, the brain will eventually disregard the image of one eye. If the eye turn is constant, the ignored eye often becomes amblyopic (lazy-eye) from non-use.
Coordination of the eyes and their ability to work together as a team is precursor to normal binocular (two-eyed) vision. This usually develops in the first six years of life. Failure of the eyes to adjust properly can lead to strabismus. The underlying cause may be hereditary factors, mechanical(muscle) or neurologic anomalies. Often the cause is a result of inappropriate retinal stimulation due to refractive (eyeglass) problems.
Parents are often the first to note the cosmetic appearance of the “crossed-eye.” Children under six are the ones most affected by strabismus, but it often appears between birth and eighteen months. The older child may fail a school vision screening. Although fewer in number, strabismus sometimes occurs in adults, but this is usually the result of diabetes, a stroke or tumor. The most important diagnostic tool is the history as this allows the doctor to know the age of onset, duration of turning, family history of strabismus and a medical history. The eye doctor will then attempt to rule out amblyopia, uncorrected refractive error and amount of deviation. The doctor should dilate the eyes to make sure that there is no hidden eye disease causing the strabismus.
A common misconception is that a child will outgrow an eye turn. In fact the condition often gets worse without treatment. Due to the different causes of strabismus the specific treatment is dependent on the type and cause. Strabismus can be treated at any age. Some factors favor younger patients while compliance and motivation are more favorable with adults. Treatment usually consists of prescription eyeglasses, vision therapy (eye-exercises), surgery or a combination of the three. The prognosis of both cosmetic (alignment) and functional (seeing) success is enhanced with active vision therapy. Surgery may cosmetically straighten the eyes but does not typically improve visual function.
Whether it is constant or intermittent, strabismus always requires appropriate evaluation and treatment. When concerned, a thorough eye examination by a pediatric optometrist is recommended by age three to investigate and rule out any possibility of strabismus. Regular visits to your family optometrist will ensure a lifetime of healthy eyes and good vision.