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V.M. Hill, D. Yang, R.W. Hertle, D.J. Stevens; Gaze–Dependent, Time Restricted Visual Acuity in Patients with Infantile Nystagmus Syndrome (INS) . Invest. Ophthalmol. Vis. Sci. 2004;45(13):2519.
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Purpose: We report a new method of measuring visual function in INS and controls by demonstrating the effects of gaze angle and time restriction on optotype recognition. Methods: This was a prospective analysis. Binocular best–corrected acuity was measured using a staircase design of Sloan single–surrounded optotypes on a computer screen. The heads of subjects were fixed such that multiple gaze angles to +/–30 degrees were achieved. Acuity was tested without any time restriction (NTRA) and was repeated with 550 msec duration for each letter in a time restriction paradigm (TRA) at each gaze angle. A paired t test was performed for all patients to compare NTRA and TRA data across respective gaze angles. Results: Gaze dependent visual acuity (GDVA) was best matching the preferred head posture in 15/16 patients in the NTRA and all patients in the TRA. GDVA was equal across gaze in all controls in the NTRA and TRA paradigms. Log values of TRA were significantly decreased relative to NTRA at horizontal gaze angles away from the null position in INS patients while there were no gaze angle difference among controls (P <0.04). Conclusions:Optotype recognition was shown to be dependent on gaze angle in INS patients versus normal controls. GDVA with and without time restrictions may therefore be useful measures in both a clinical setting and as clinical trial outcomes.
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