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Shaobo Lei, Herbert C. Goltz, Mano Chandrakumar, Agnes M. F. Wong; Full-field Chromatic Pupillometry for the Assessment of the Postillumination Pupil Response Driven by Melanopsin-Containing Retinal Ganglion Cells. Invest. Ophthalmol. Vis. Sci. 2014;55(7):4496-4503. doi: 10.1167/iovs.14-14103.
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The postillumination pupil response (PIPR) is produced by intrinsically photosensitive retinal ganglion cells (ipRGCs). We aimed to refine the testing conditions for PIPR by investigating whether a greater PIPR can be induced using full-field light stimuli of shorter duration and lower intensity than that produced by existing protocols that use central-field stimuli.
Pupil response was recorded with an eye tracker in 10 visually-normal subjects. Red and blue light stimuli were presented using a Ganzfeld system. In Experiment 1 (intensity trials), PIPR was induced using 1-second full-field stimuli of increasing intensities from 0.1 to 400 cd/m2 (11 steps). For comparison, PIPR also was induced using a 60° × 90° central-field blue stimulus of 400 cd/m2. In Experiment 2 (duration trials), PIPR was induced using 100 and 400 cd/m2 full-field stimulus of increasing duration from 4 to 1000 ms (10 steps).
Results indicated that PIPR increased monotonically with increasing stimulus intensity. Full-field stimulation using blue light at 400 cd/m2 intensity induced significantly more sustained PIPR than central-field stimulation (P = 0.001). In addition, PIPR increased as the stimulus duration increased from 4 to 200 ms; however, no further increase in PIPR was observed when the duration increased from 400 to 1000 ms.
Compared to existing central-field protocols, larger PIPR can be induced with a full-field stimulus with lower intensity and shorter duration, indicating that PIPR is a function of stimulus intensity, stimulus duration, and retinal area stimulated. The testing protocol can be refined with this new knowledge to target particular clinical populations.
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