Optometry and Vision Sciences - Research Publications
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ItemNo Preview AvailableFactors influencing the experience of oscillopsia in infantile nystagmus syndrome(ASSOC RESEARCH VISION OPHTHALMOLOGY INC, 2008-08)PURPOSE: Perceptual instability in infantile nystagmus syndrome (INS) has been reported occasionally. This study was conducted to examine the factors that influence perceptual stability in 18 individuals with INS. METHODS: The subjects were instructed to look continuously 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 then both LEDs off. Subjects then reported what they perceived. Five trials were conducted per contrast image. Eye movements were recorded with a limbal tracker. After testing, each subject completed a questionnaire to determine whether they ever had or were presently experiencing oscillopsia. RESULTS: Sixteen of 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% to 60%; background only, 15% to 30%; both, approximately 15%; and LED only, approximately 10%. Over all trials, 14/18 and 13/17 subjects experienced oscillopsia for the low- and high-contrast images, respectively (i.e., four subjects never experienced oscillopsia). The background was frequently seen moving when both images were displayed, regardless of contrast and/or condition. Trials with and without oscillopsia did not differ between the foveation periods. CONCLUSIONS: Subjects with INS 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 a subject's perception differently.
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ItemSaccadic Eye Movement Characteristics in Adult Niemann-Pick Type C Disease: Relationships with Disease Severity and Brain Structural Measures(PUBLIC LIBRARY SCIENCE, 2012-11-30)Niemann-Pick Type C disease (NPC) is a rare genetic disorder of lipid metabolism. A parameter related to horizontal saccadic peak velocity was one of the primary outcome measures in the clinical trial assessing miglustat as a treatment for NPC. Neuropathology is widespread in NPC, however, and could be expected to affect other saccadic parameters. We compared horizontal saccadic velocity, latency, gain, antisaccade error percentage and self-paced saccade generation in 9 adult NPC patients to data from 10 age-matched controls. These saccadic measures were correlated with appropriate MRI-derived brain structural measures (e.g., dorsolateral prefrontal cortex, frontal eye fields, supplemental eye fields, parietal eye fields, pons, midbrain and cerebellar vermis) and with measures of disease severity and duration. The best discriminators between groups were reflexive saccade gain and the two volitional saccade measures. Gain was also the strongest correlate with disease severity and duration. Most of the saccadic measures showed strongly significant correlations with neurophysiologically appropriate brain regions. While our patient sample is small, the apparent specificity of these relationships suggests that as new diagnostic methods and treatments become available for NPC, a broader range of saccadic measures may be useful tools for the assessment of disease progression and treatment efficacy.
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ItemExamining the pseudo-standard web search engine results page(Queensland University of Technology, 2006-12-01)