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FACTORS INFLUENCING THE EXPERIENCE OF OSCILLOPSIA IN INFANTILE NYSTAGMUS SYNDROME.

Cham KM, Anderson AJ, Abel LA

Optometry & Vision Sciences, University of Melbourne, 912/1 Bouverie st, Carlton, Victoria, 3053, Australia.

Purpose: Since perceptual instability in infantile nystagmus syndrome (INS) is reported occasionally, we examined the factors influencing perceptual stability in eighteen individuals with INS. Methods: Subjects were instructed to continuously look at a fixation LED centered in an image (38 degrees x 32 degrees ) at two luminance levels (3.25 and 0.46 cd/m(2), with 21% and 96% contrast, respectively) throughout all trials. A trial consisted of the fixation LED on, followed by a peripheral LED on, and both LEDs off. Subjects then reported what they perceived. We conducted five trials per contrast image. Eye movements were recorded with a limbal tracker. After testing, each subject completed a questionnaire to determine if they ever had or were presently experiencing oscillopsia. Results: 16/18 subjects reported experiencing oscillopsia on the questionnaire. In the laboratory, the percentages of trials with perceptions of motion of the LED and background were as follows: neither, 45-60%; background only, 15-30%; both, ~15%, and LED only, ~10%. Over all trials, 14/18 and 13/17 subjects experienced oscillopsia for the low- and high-contrast image respectively (i.e. 4 subjects never experienced oscillopsia). The background was frequently seen moving for both images regardless of contrast and/or condition. Trials with and without oscillopsia did not differ when comparing foveation periods. Conclusions: INS subjects may experience spatially inhomogeneous oscillopsia under certain viewing conditions. The physical attributes of the stimulus, repeated trials, different conduction times, and the role of divided attention may influence the perception of a subject differently.

Published 18 April 2008 in Invest Ophthalmol Vis Sci.
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