Dissociated horizontal deviation after surgery for infantile esotropia: clinical characteristics and proposed pathophysiologic mechanisms.

OBJECTIVE To examine the results of reversed fixation testing in patients who develop consecutive exotropia after surgery for infantile esotropia. METHODS The reversed fixation test was performed prospectively in 28 patients who developed consecutive exotropia after surgery for infantile esotropia. All patients were assessed for adduction weakness, latent nystagmus, dissociated vertical divergence, and neurologic disease. RESULTS A positive reversed fixation test, indicating the presence of dissociated horizontal deviation, was found in 14 of 28 patients (50%) with consecutive exotropia. In patients with dissociated horizontal deviation, the exodeviation was usually smaller with the nonpreferred eye fixating than with the preferred eye fixating, and smaller with the preferred eye fixating than during periods of visual inattention or under general anesthesia. Dissociated horizontal deviation correlated with the findings of dissociated vertical divergence, but not with asymmetric adduction weakness, latent nystagmus, or neurologic disease. CONCLUSIONS Dissociated horizontal deviation is a clinical expression of dissociated esotonus. The common clinical presentation of dissociated horizontal deviation as an intermittent exodeviation of 1 eye results from the superimposition of a dissociated esotonus on a baseline exodeviation.