Gaze-dependent and time-restricted visual acuity measures in patients with Infantile Nystagmus Syndrome (INS)

Abstract

We report a new method of measuring visual function in patients with INS by demonstrating the effects of eccentric gaze and forced time restriction on optotype recognition. Cross-sectional, comparative case-series. No-time-restricted acuity (NTRA) and time-restricted acuity (TRA) for 19 patients and 18 controls were measured at multiple horizontal gaze angles. INS patients showed a significant lower visual acuity than controls (P < 0.0001). The TRA were significantly decreased in most gaze positions relative to NTRA in INS patients (P = 0.03) while there were no difference among controls. About half of the INS patients showed that their best visual acuity was gaze dependent, matching the preferred head posture in both NRTA and TRA paradigms. Gaze-dependent visual acuity tested with and without time restriction may be a useful measure of visual function in INS patients and could be used in interventional clinical trials.