Esotropia is a type of strabismus (eye misalignment) in which one or both eyes cross or turn inward.

There are two main types of esotropia. The first is infantile esotropia and it appears at a very early age, usually by 6 to 12 months. The second type, acquired esotropia, appears any time from 1 to 8 years of age, but usually between 2 and 5 years old.

Infantile esotropia may initially seem intermittent or small, but quickly becomes a constant crossing of the eyes which is fairly large in magnitude. Most of these infants cross both eyes equally, but occasionally will cross one eye more frequently or more severely than the other.

The cause of infantile esotropia is unknown, but it runs in families and there is a genetic predisposition. Treatment for infantile esotropia is almost always surgical. This involves loosening or weakening the inner (medial rectus) muscles in order to straighten the eyes. This type of esotropia can almost never be corrected with glasses alone, although if a child is extremely far sighted, glasses may be required in addition to surgery.

If the child crosses one eye more than the other, this may be a sign of amblyopia or lazy eye. Amblyopia is the word for the poor vision that develops in a drifting eye because it is not used enough. In this case, patching of the stronger eye may correct the vision in addition to surgery to straighten the eyes. The worse the vision, the more patching required to correct it. Amblyopia or "lazy eye" occurs more frequently in acquired esotropia than in infantile esotropia.

Acquired esotropia occurs in children who develop crossed eyes after age 1 or 2. In many of these children the crossing is caused by a refractive error or farsightedness and can be corrected by with glasses.

Farsightedness (hypermetropia) causes the eyes to cross because the child has to strain to focus and see. Glasses eliminate the need to focus and thus correct the crossing. Occasionally bifocal glasses are needed if the eyes cross more when looking close rather than a distant objects. Even if glasses do correct the crossing, the eyes will still cross when the glasses are not being worn.

Sometimes glasses will not fully correct acquired esotropia and surgery on the eye muscles may be required. Surgery is more likely in children who have had uncorrected esotropia for a long time, and in children who have developed amblyopia or "lazy eye". If lazy eye is present, patching of the stronger eye will be required in addition to glasses and/or surgery.

If glasses do not correct the crossing in six to eight weeks, surgery generally will be recommended. Most children whose eyes are straightened with glasses will require glasses throughout childhood, although many of them may outgrow the glasses when they reach 7 to 8 years old. At any time during childhood if the glasses are no longer straightening the eyes, surgery may be recommended.

by  David R. Weakley, Jr., M.D.

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