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G. Jean–louis, F. Zizi, D.R. Lazzaro, A.H. Wolintz, J. Tsai, C. Haines, A. Harris; Association Of Retinal Perfusion And Endogenous Melatonin . Invest. Ophthalmol. Vis. Sci. 2006;47(13):2105.
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© ARVO (1962-2015); The Authors (2016-present)
This study tested the hypothesis that reduction in retinal perfusion pressure is associated with phase advances in endogenous melatonin rhythms of older adults.
Eleven volunteers (mean age: 66.82 ± 4.21 years) provided complete data for the present study. Each was interviewed to obtain demographic and health–related data. They wore an actigraph (Actiwatch–L) to monitor ambient illumination and sleep. On the last 24 hours of the recording, fractional urine samples (n=10) were acquired for melatonin (aMT6s) assays. Cosine analyses yielded the mesor and acrophase for illumination and melatonin time series. Volunteers were then assessed with the Heidelberg Retina Flowmeter to obtain data on retinal capillary blood volume. To derive blood flow and volume at the papilla, we employed a method using a 40X40–pixel retinal area showing no eye–motion artifacts or visible blood vessels; a single pixel was manipulated to obtain 1600 data points from which poorly illuminated values (areas of zero flow) were discarded.
Most of the volunteers rated their health status as good (70%) and were satisfied with their habitual sleep (90%). None received an eye diagnosis, but 28% were visually impaired using standard criteria. The average BMI was 27.50 ± 7.90kg/m2; actigraphic sleep duration and depression scores averaged 7.75 ± 1.80hrs and 6.45 ± 3.47 (GDS), respectively. Median illumination and aMT6s excretions were 636lux and 308ng/h, respectively, and the median for acrophases of illumination and aMT6s were 13.02hours and 2.80hours, respectively. We found an inverse correlation of the area of reduced retinal blood flow (zero flow) to the timing of aMT6s (rp=–0.65, p=0.04) and to daily illumination levels (rp=–0.74, p=0.01); age effects were adjusted. Further analysis suggests a direct relationship between blood flow volume and both aMT6s mesor (rp=0.43) and timing (rp=0.29), but results were not statistically significant. Reduced retinal blood flow was not significantly correlated to aMT6s mesor or illumination timing.
Results suggest that age–related ocular pathologies, potentially affecting blood flow to the retina and to the optic nerve head could reduce photic transmission. Peripapillary retinal damage might have independent effects on the circadian rhythm of melatonin, as neither ambient illumination level nor sleep duration affected the relationships.
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