Abstract
Purpose: :
The purpose of this report is to summarize and characterize long term, clinical and electrophysiological effects following extraocular muscle surgery in a prospective case series of patients with the specific ocular motor disorder of INS.
Methods: :
This is a prospective, non–comparative, interventional case series of 75 patients with INS all of whom had surgery on all of their previously unoperated four horizontal extraocular muscles. The indications for surgery included an eccentric gaze null position, strabismus alone, strabismus plus an eccentric gaze null position and nystagmus alone. Outcome Measures Included: Pre– and Post–Operative Binocular Best Optically Corrected Acuity (BCA) in all 75 patients, Anomalous Head Posture (AHP) in 36 patients, Expanded Nystagmus Acuity Function (NAFX) in 15 patients, Null Zone Position (NZP) and Null Zone Width (NZW) in 38 patients, Foveation Time (FOV) in 15 patients, Gaze Dependent Visual Acuity (GDVA) in 6 patients and The National Eye Institute Visual Function Questionnaire (VFQ) in 15 patients.
Results: :
After at least 12 months, INS patients remained improved in BCA, AHP, NZP, NZW, NAFX, FOV, GDVA and VFQ measures. BCA increased .1 LogMar in 71 %, .2 LogMar in 53 % and .3 LogMar in 15% of patients. Patients <8 years old improved more than patients > 8 years in BCA (P=.01), AHP (P=.04), and NZP (P=.002); but not for NZW (P=.88). In those operated on for an AHP with or without associated strabismus the AHP improved significantly.
Conclusions: :
This report adds to the evidence that surgery on previously unoperated horizontal extraocular muscles in patients with INS favorably changes their nystagmus. The effect of surgery on the INS oscillation is independent from mechanical repositioning of the eyes or muscles. The nystagmus changes that result from surgery on the extraocular muscles in patients with INS helps to improve vision and visual functions.
Keywords: nystagmus • eye movements • strabismus: treatment