Chapter 2: What is Strabismus?
A Patient & Parent Guide to Strabismus Surgery
George R. Beauchamp, M.D.
Strabismus refers to eyes that are out of alignment. The eyes maybe converged (crossed), diverged (outwardly deviated), vertically (one eye higher than the other) or torsionally misaligned (one or both eyes rotated inwardly or outwardly). These planes of alignment (and misalignment) are like the types of movement of boats and airplanes—sometimes called yaw, pitch and roll.
- Crossing (or deviation of one or both eyes toward the nose) is called esotropia.
- Outward (toward the ear) deviation of one or both eyes is called exotropia.
- Vertical deviation or divergence of the eyes is called hypertropia (higher) or hypotropia (lower).
- Torsional (rotational or tilting) misalignment is called cyclotropia.
Misalignment of the eyes may be constantly manifest—called a tropia—such as above, esotropia, esotropia, etc. Or the deviation may be intermittent, called intermittent esotropia, etc. Surgery may be appropriate for either constant or intermittent deviations, depending on a number of factors, including magnitude of the deviation, constancy or frequency of the misalignment, and the presence of other signs and symptoms.
One relatively simple way to think about strabismus is the concept of the position of rest of the eyes. Therefore, the problem of strabismus is not necessarily that of an abnormal eye. The problem is the angle of deviation between the two. Consequently, the eye that “drifts” is not necessarily abnormal; quite simply, the dominant or preferred eye is “straight” – that is, directed (pointed) toward the object being viewed—while the other assumes the position of rest. The importance of this concept is to explain that to correct the problem requires eliminating this angle of deviation between the eyes. For treatment, muscles on one or both eyes may be repositioned to eliminate or diminish this angle and eliminate the strabismus.
Read Chapter 3: What Causes Strabismus?
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