Arvo Poster 2014 Shaobo V3

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<ul><li><p>Melanopsin is a photopigment allowing a small subset of retinal ganglion cells to absorb light energy directly and fire </p><p>action potential with or without synaptic input form rods and </p><p>cones. Intrinsic photo response of melanopsin-containing </p><p>retinal ganglion cells (MGCs) provides sustained irradiance </p><p>coding for non-visual photoperception functions including </p><p>circadian photoentrainment and the pupillary light response. </p><p>A sustained pupil constriction can be observed after the </p><p>offset of a bright blue light stimulus. This post-illumination </p><p>pupil response (PIPR) is produced by MGC, and can be </p><p>measured by chromatic pupillometry. Measuring PIPR holds </p><p>promise as a novel tool to assess MGC function. Current </p><p>testing protocols use central-field stimulation and require a </p><p>very bright light of long duration which can be difficult for </p><p>some subjects. We test the hypothesis that a consistent </p><p>PIPR can be induced with full-field blue light stimuli of </p><p>shorter duration and lower intensity than with central-field </p><p>stimulation. </p><p>IntroductionIntroduction </p><p>Apparatus: </p><p>Full-field and central-field light stimulation were presented </p><p>with a Colordome Ganzfeld bowl originally designed for </p><p>ERG testing. </p><p>Pupillary light response was monitored with a video based </p><p>eye tracker at 60Hz. </p><p>MethodsMethods </p><p>Experimental Conditions (cont.): </p><p>For each of the intensity and duration steps, a red flash was </p><p>presented first followed by a blue flash 45 s after the offset of </p><p>the red flash. Participants were provided with a short break at </p><p>45 s after the offset of the blue flash to allow the pupil size to </p><p>return to baseline and to prevent fatigue. </p><p>Measurement and Data Analysis: </p><p>Pupil size data were normalized to baseline calculated from </p><p>the mean pupil size during a 1 s period before the onset of </p><p>each stimulus. </p><p>Primary Outcome Measure </p><p>PIPR: mean of the normalized pupil size over a 20 s period </p><p>from 10-30s after the offset of light stimuli (smaller number </p><p>means greater pupil constriction). </p><p> 400 cd/m2, full-field blue stimulus induced significantly </p><p>larger PIPR than central-field blue stimulus of the same </p><p>intensity. </p><p> PIPR to red flashes did not differ significantly full-field vs. </p><p>central-field. </p><p> No further increase in PIPR was observed when the </p><p>duration increased from 400-1000 ms. </p><p> 400-1000 ms, 400 cd/m2 blue full-field stimuli induced </p><p>significantly greater PIPR than 1000 ms blue central-field </p><p>stimulus of the same duration. </p><p> Full-field stimulation is more effective that central-field </p><p>stimulation in inducing PIPR, suggesting that PIPR is a </p><p>function of stimulus intensity, duration and area. </p><p> This study is the first to demonstrate that saturating PIPR </p><p>up to 30 seconds post illumination can be induced in vivo </p><p>with a strong blue flash lasting only a few hundred </p><p>milliseconds. </p><p> This updated understanding of the relation between PIPR </p><p>and stimulus intensity, duration and area will allow </p><p>investigators to tailor their PIPR testing paradigm to target </p><p>a specific research question, and greatly facilitate the </p><p>development of a convenient and comfortable technique to </p><p>assess MGCs function for emerging clinical use. </p><p>shao-bo.lei@sickkids.ca </p><p>ConclusionsConclusions </p><p>Contact InformationContact Information </p><p>FullFull--Field Field ChChroromamatictic Pupillometry in the Assessment of the PostPupillometry in the Assessment of the Post--Illumination Pupil ResponseIllumination Pupil Response </p><p> Driven by MelanopsinDriven by Melanopsin--Containing Retinal Ganglion CellsContaining Retinal Ganglion Cells </p><p> 1Shaobo Lei, 1,2H.C. Goltz, 1M. Chandrakumar, 1,2,3A.M.F. Wong </p><p> 1Program in Neuroscience &amp; Mental Health, Hospital for Sick Children; Department of Ophthalmology and Vision Sciences, 2University of Toronto &amp; 3Hospital for Sick Children, Toronto Canada </p><p>No.4110 - A0098 </p><p>Session: 413 </p><p>Participants: </p><p>10 visually-normal adult subjects (mean age: 31 years, </p><p>range 22 56), only right eyes were stimulated and </p><p>recorded, left eyes were patched during recording. </p><p>Experimental Conditions: </p><p>Experiment 1 (intensity trials): After 10 min dark adaptation, </p><p> PIPR was induced with alternating red (64010 nm) and </p><p>blue (46717 nm), 1-second full-field stimuli of increasing </p><p>intensity from 0.1 to 400 cd/m2 (11 steps) . For comparison </p><p>with a previously published protocol, a 6090 central-field </p><p>blue stimulus at 400 cd/m2 was also presented for 1 second. </p><p>Experiment 2 (duration trials): 10 min dark adaptation, 100 </p><p>cd/m2 and 400 cd/m2, red and blue full-field stimulations of </p><p>increasing duration from 4-1000 ms were presented </p><p>alternately. 100 cd/m2 and 400 cd/m2 trials were conducted </p><p>on different days. </p><p>* Mean (n=10) normalized post-illumination pupil response (PIPR) tracings in response to 1 s stimulation of varying intensity from 10 visually-normal participants. </p><p> PIPR to full-field blue stimulation increased monotonically </p><p>with increasing stimulus intensity. </p><p> Red light (internal reference) induced no or minimal PIPR </p><p>at all intensity level. </p><p>Results: Results: Experiment 1 (intensity Experiment 1 (intensity trials)trials) </p><p>* Comparison of PIPR induced using 400 cd/m2 central-field stimuli (dashed line) vs 100-400 cd/m2 full-field stimuli (solid lines) </p><p> PIPR in response to 400 cd/m2 increased as the duration of </p><p>stimulus increased from 4-200 ms. </p><p>* Mean PIPR to 100 cd/m2 and </p><p>400 cd/m2 full-field stimulation </p><p>of varying duration from 10 </p><p>visually-normal observers. </p><p>Results: Results: Experiment 2 (duration trials)Experiment 2 (duration trials) </p><p>* comparison of PIPR to full-field blue stimuli of 400 cd/m2 intensity of the 6 longest duration steps (100, 200, 400, 600, 800, and 1000 ms. </p><p>*Authors have no commercial interest to disclose. </p><p>Statistic Analysis </p><p>One-way ANOVA with post hoc corrected for pairwise </p><p>multiple comparisons using the TukeyKramer method. </p><p>Full-Field vs. Central-field Stimulation </p><p>* Intensity-response function of PIPR to full-field stimulation vs. PIPR to 1s, 400 cd/m2 central-field stimuli </p><p>* Duration-response function of PIPR to full-field stimulation vs. PIPR to 1s, 400 cd/m2 central-field stimuli </p></li></ul>