PREOPERATIVE ALTERNATE OCCLUSION DECREASES MOTION PROCESSING ABNORMALITIES IN INFANTILE ESOTROPIA

We have examined the effects of preoperative, full-time alternate occl usion on the development of visual motion processing mechanisms. Motio n visual evoked potentials (MVEPs) were recorded longitudinally in 14 infantile esotropia patients during the course of standard preoperativ e occlusion therapy. The MVEP in these patients was initially asymmetr ic in a fashion consistent with a nasalward/temporalward response bias , with a motion asymmetry significantly higher than that of age-matche d normals. The magnitude of the developmental motion asymmetry decline d significantly after an average of 24 weeks of alternate occlusion. T his result implies that the binocular motion-sensitive cells underlyin g the MVEP retain some degree of plasticity up to at least 1 year of a ge. Our data suggest further that the persistence of motion asymmetrie s in untreated infantile esotropia patients is maintained by an active process that can be disrupted by alternate occlusion. Alternate occlu sion apparently eliminates a form of abnormal binocular interaction th at supports the persistence of the motion asymmetry. We propose that o ne of the necessary pre-conditions for symmetricization of motion proc essing in infantile esotropia is the absence of abnormal competitive b inocular interactions.