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D. Yang, R.W. Hertle; Gaze Dependent Optotype Recognition in Infantile Nystagmus (INS) Patients versus Normal Subjects . Invest. Ophthalmol. Vis. Sci. 2003;44(13):2740.
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Purpose: To report a new method of measuring visual function in patients with infantile nystagmus syndrome (INS). The visual function measured was optotype acuity with respect to gaze. We measured this function in both controls and patients with and without restricting the time that optotypes were displayed at varying gaze angles. Methods: Patients and controls were asked to binocularly identify Sloan single-surrounded optotypes on the center of a computer screen while their heads were fixed at different angles horizontally and vertically so that different gaze angles were created. This was accomplished without (no time restricted acuity, NTRA) and with a time restriction (time restricted acuity, TRA). 550 msec was the time used for the presentation duration of each letter in the TRA paradigm. A modified staircase design was used to test threshold and final acuity at each gaze angle. Data at each position of gaze was collected, graphically displayed and statistical comparison of patients to controls across gaze was accomplished. Results: We studied 10 normal subjects (ages 21-50, mean 34) and 9 patients with INS (ages 7-57, mean 27). There were no differences in acuity among or between control subjects at various gaze angles in either the TRA or NRTA paradigm (Figure, Top Traces). INS patients showed changing acuity that was dependent on gaze angle and these changes were more sensitive in the RTA paradigm (Figure, Bottom Traces). Conclusions: We have shown that both gaze angle and time affect optotype recognition in patients with INS. These factors may be important in determining visual function in the INS population and may be useful outcome measures in patients with INS entering clinical trials. View OriginalDownload SlideView OriginalDownload Slide
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