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Anthony E Felder, Norman P Blair, Mahnaz Shahidi; Temporal dynamics of inner retinal vasculature and oxygen extraction fraction during light flicker stimulation in humans. Invest. Ophthalmol. Vis. Sci. 2016;57(12):3749.
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© ARVO (1962-2015); The Authors (2016-present)
Light flicker stimulation increases retinal neural activity, augments retinal vessel diameter (D), alters retinal vascular oxygen saturation (SO2) and changes inner retinal oxygen extraction fraction (OEF). The purpose of the study was to report the temporal dynamics of simultaneously measured D, SO2 and OEF during light flicker stimulation in humans.
Our previously described optical imaging system for retinal oximetry during light flicker was modified to accommodate a customized image acquisition protocol. Retinal images were acquired in five healthy subjects (age=65±6 yrs) at every 10s over a time-course consisting of 30s before light flicker, 60s during light flicker and 30s after light flicker termination. A customized image analysis algorithm measured arterial and venous D (DA and DV) and SO2 (SO2A and SO2V), and calculated inner retinal OEF ((SO2A- SO2V)/SO2A) at each time point. Repeatability was determined by the coefficient of variation of three repeated measurements before light flicker. Metric ratios (DAR, DVR, SO2AR, SO2VR and OEFR) were calculated as the metric value at each time point divided by the mean metric value before light flicker, and then averaged over all subjects. Temporal dynamics during light flicker were quantified by linear regression analysis.
Repeatability of DA, DV, SO2A, SO2V and OEF measurements before light flicker was 1%, 1%, 1%, 4% and 5%, respectively. DAR, DVR and SO2AR did not change significantly during light flicker (R≤0.84, P≥0.07, N=6) and mean values were 1.01±0.01, 1.05±0.01 and 1.01±0.01, respectively. During 60s of light flicker, SO2VR increased significantly from 1.00 to 1.09 (R=0.95, P=0.01, N=6), and consequently, OEFR decreased significantly from 1.01 to 0.85 (R=0.99, P=0.003, N=6). Mean values of DAR, DVR, SO2AR, SO2VR and OEFR at 30s after the termination of light flicker were 0.97±0.06, 1.02±0.03, 1.01±0.02, 1.00±0.10 and 1.01±0.12, respectively.
The temporal dynamics of simultaneously measured D, SO2 and OEF during light flicker stimulation were reported in healthy human subjects for the first time. Inner retinal OEF decreased linearly during light flicker and recovered within 30s of light flicker termination. Quantitative assessment of the temporal dynamics of inner retinal OEF during light flicker stimulation will improve knowledge of retinal oxygen metabolism in health and disease.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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