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Frederick T Collison, Jason C Park, J Jason McAnany, Gerald A Fishman; Full-field luminance thresholds, light discomfort thresholds, and pupillary light responses in CEP290 Leber congenital amaurosis patients.. Invest. Ophthalmol. Vis. Sci. 2014;55(13):1421.
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To investigate full field visual function and pupillary responses in patients with non-syndromic CEP290 Leber congenital amaurosis (LCA-CEP290), using three tests that can be performed by patients with poor fixation.
Five patients (ages 9, 24, 31, 39 and 36 years) with LCA-CEP290 participated in the study. Stimuli for all three tests (the full-field stimulus test [FST], pupillometry, and light discomfort threshold testing) were generated by the Diagnosys ColorDome ganzfeld, utilizing long- and short-wavelength stimuli. Both eyes of all five patients were tested with the FST, a measure of luminance threshold. The pupillary light reflex (PLR) was measured from all five subjects in one eye with 1-second duration stimuli, using a published method that targets rod, cone, and melanopsin function. The four older patients were tested for dark-adapted light discomfort thresholds. The light discomfort test utilized a 2-second stimulus that was increased in luminance step-wise from -0.9 to 3.6 log cd/m2 in 0.3-log intervals. Subjects terminated the test when they found the stimulus to be "uncomfortable."
FST thresholds were cone-mediated and elevated between 6 and 7 log units from the normal dark adapted short-wavelength threshold in patients 1-4. FST threshold was non-measurable in Patient 5, who had inconsistent bare light perception. PLR results were inconclusive in the youngest patient (patient 1) due to pupillary fluctuations during testing. The rod-mediated PLR was absent in patients 2-5. The cone-mediated PLRs were borderline abnormal in patients 2-4, and absent in patient 5. The melanopsin-mediated PLRs were measurable in patients 2-5. Subjects 2-4 all were found to have light discomfort thresholds that were lower to short-wavelength stimuli versus long-wavelength stimuli.
Our FST findings of cone-mediated responses are consistent with a published study that showed most LCA-CEP290 patients have either cone-mediated or mixed (rod and cone-mediated) FST thresholds. To our knowledge, this is the first report of pupillometry and light discomfort threshold testing in LCA-CEP290. Light-discomfort thresholds that are lower to short wavelength light suggest the influence of melanopsin on light discomfort in these patients with no detectable rod responses on FST and pupillometry testing.
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