Clinical and electrophysiological effects of extraocular muscle surgery on patients with Infantile Nystagmus Syndrome (INS).

The purpose of this report is to summarize clinical and electrophysiological effects of extraocular muscle surgery in patients with INS. Our hypothesis is that surgery on the extraocular muscles of patients with INS changes their nystagmus resulting in improved vision and visual functions. All patients had all four virgin horizontal recti operated on, either for strabismus alone, nystagmus alone, for a head posture due to an eccentric null zone alone or for a head posture due to an eccentric null zone plus strabismus. All patients have been followed for at least 12 months. Subjective outcome measures include the pre- and post-operative binocular best optically corrected null zone acuity (NZA) in 75 patients and gaze dependent acuity (GDA) in 12 patients. Objective outcome measure included null zone width (NZW) in 75 patients. The results are summarized as follows: NZA increased .1 LogMar or greater in 75% with those patients <or=8 years significantly better. Subjective GDA and NZW measured from eye movement recordings showed persistent, significant increases. This report adds to the evidence that surgery on the extraocular muscles in patients with INS has independent neurological and visual results, from simply reposition the head, eye(s) or visual axis.