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Frederick T. Collison, Dingcai Cao, J. J. McAnany, Mohamed A. Genead, Gerald A. Fishman; Pupillary Responses To Offset And Onset Of Isolated Rod And Cone Stimuli Using A 4-Primary Photostimulating Method. Invest. Ophthalmol. Vis. Sci. 2012;53(14):4823.
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© ARVO (1962-2015); The Authors (2016-present)
The purpose of the current study was to investigate the OFF-transient pupillary constriction, which is thought to be non-melanopsin mediated, with isolated rod and cone stimulation at the same light level.
A commercially available four-primary stimulator (Diagnosys ColorDome) was used to generate isolated rod (25% contrast), and cone luminance (L+M+S 20% contrast), at 10 or 100 cd/m2, as well as S-cone (90% contrast) at 100 cd/m2. Pupil responses to stimulus onsets and offsets were recorded in six normal subjects using a frame-mounted infrared pupillometer (Arrington Research). Each trial started with a 30 second adaptation to the background (L+M+S+Rod), followed by alternated stimuli (10 sec) and background (10 sec). The percentages of constriction within a two second window of any light change were computed and differences among the conditions were evaluated using non-parametric Wilcoxon signed-rank tests.
For isolated S-cone stimuli at 100 cd/m2, the pupil constriction to decrement was greater than to increment (15.8% vs. 8.3%, p = 0.028). For other stimulus types, increment constriction was greater than decrement constriction at both 10 cd/m2 and 100 cd/m2 (p = 0.028). A small constriction to decrement was found for both rods (5.2% at 10 cd/m2, p = 0.035; 7.7% at 100 cd/m2, p = 0.028) and L+M+S cones (4.0% at both light levels, p = 0.028).
The paradoxical transient pupil constriction to overall light decrease found in some patients with retinal dysfunctions has previously been observed in subjects with normal vision using chromatic stimuli. Using our isolated stimuli, we reliably elicited transient pupil constrictions to rod, L+M+S cone and S cone onset, as well as to S cone offset. Small constrictions were found to rod and L+M+S cone offset. Our method may have applications in differentiation of rod pathway dysfunction from cone pathway dysfunction, particularly in patients who exhibit the paradoxical pupillary response.
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