Clinical and electrophysiological outcomes after eye muscle surgery in 81 adults with infantile nystagmus syndrome

Purpose: To characterize the effects of eye muscle surgery on patients older than 18 years with infantile nystagmus syndrome (INS) who have had only optical treatment. Methods: This was a prospective, single-center, interventional case series analysis of clinical and electrophyisological data before and after surgery. Outcome measures included: Clinical characteristics, surgical procedure, and preoperative and postoperative binocular best corrected visual acuity (BCVA) in the null position, anomalous head posture (AHP), contrast sensitivity, strabismic deviation, and nystagmus acuity function (NAFX). Postoperative data used were collected for a minimum of 12 months after surgery. Parametric and non-parametric statistical analysis of the outcome measures was performed. Results: Ages ranged from 18 to 72 years (average: 36 years) and follow-up from 12 to 74 months (average: 26 months). A surgical algorithm of nine separate procedures involving at least two recti muscles on each eye was used for each patient. Most patients had associated systemic and/or ocular diagnoses, including albinism (35%), amblyopia (23%), optic nerve or retinal disorders (48%), refractive error (80%), AHP (44%), aperiodicity (27%), and strabismus (69%). There were no serious surgical complications, with a reoperation rate of 12%. There were significant group mean increases in BVCA, AHP, contrast sensitivity, strabismic deviation, and NAFX after surgery. Sixty percent of patients who were legally ineligible for driving prior to surgery became eligible after eye muscle surgery. Conclusions: Adult patients with INS showed sustained improvement in many afferent and efferent measures of visual function after eye muscle surgery.