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The use of an abnormal head posture to place the eyes in a position of least nystagmus is well known to us all. Recently we have begun to realize that some patients are using their convergence mechanisms to dampen their nystagmus, thus presenting with large angle esotropias. Adelstein and Cuppers' in 1966, termed this complex of esotropia and nystagmus, the "nystagmus blockage syndrome." Subsequent authors have expanded the diagnostic criteria and therapeutic regimens.2"4 This syndrome is now recognized as the "nystagmus compensation syndrome" in the English literature. The following is a summary of the diagnostic signs of the nystagmus compensation syndrome.
DIAGNOSTIC SIGNS
1. Convergent strabismus with the onset in infancy. The onset may be preceded by manifest nystagmus.4 There is usually a large variable angle superimposed on a small stable angle. The strabismus may be unilateral or alternating. The patients often appear to be cross fixating as both eyes may be held in adduction. Amblyopia is often found.
2. An abnormal head posture, toward the adducted fixing eye (Figs. 1 and 2) is generally present. This posture persists when one eye is occluded. This simulates a paralysis of both lateral recti (Figs. 3 and 4).
3. The nystagmus is reduced or absent with the fixing eye adducted. As the fixing eye attempts to abduct, the nystagmus increases and becomes manifest. On version testing, the strabismic eye will remain in adduction or follows more slowly as the fixing eye attempts abduction.
4. If the adducted eye fixates, there is no significant change in the strabismic angle in lateral gaze. However, the angle of strabismus may be reduced or eliminated in lateral gaze if the abducting eye fixates (Figs. 5 and 6).
5. When placing a large base-out prism...