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John V. Lovasik, Helene Kergoat, Marie-Jeanne Kergoat, Normand Racine, Mireille Parent; Age Affects Vasoconstriction Before Vasodilation In Retinal Vessels. Invest. Ophthalmol. Vis. Sci. 2011;52(14):6037.
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© ARVO (1962-2015); The Authors (2016-present)
The human retina is known to have both pressure regulation that keeps blood flow constant during changes in the ocular perfusion pressure, and metabolic regulation that adjusts retinal blood flow to match changes in metabolism caused by light stimulation of the retina. The present study examined the latter phenomenon in the human retina as a function of age.
Subjects in this study were 120 healthy adult volunteers, 20-80 yrs of age with 20 subjects for each decade of life. After a 15s baseline recording for a paired retinal artery and vein, real-time changes (30 fps) in vessel diameter were recorded with a Retinal Vessel Analyser (Imedos) during and after three consecutive 60s flicker-60s recovery intervals. The three stimulus-recovery intervals for each subject were averaged after normalizing to the baseline just prior to each flicker. Then the data for each cohort of 20 subjects were group averaged to provide the amplitude and temporal properties of the response profile by age group.
In veins, flicker first elicited a rapid dilation followed by a much slower dilation that continued to a maximum of ~8%. After Flicker, veins constricted monotonically towards baseline. The arterial response paralleled the veins but the maximum dilation was ~6% and recovery from flicker was more complete. However, these response profiles showed distinctive changes with age. While the initial rate of dilation remained fixed with age in arteries and veins, the maximum arterial dilation decreased by 2% at age 70. The most prominent age change was in the recovery interval. In the 20s, arteries typically overshot then recovered baseline. This overshoot slowly decreased with age until the 60s & 70s where constriction failed to recover baseline. Venous constriction in recovery was ~1% short of baseline up to the 60s, after which it decreased to 2% short of baseline.
The retinal vasodilatory response to flicker is maintained up to 60 years of age while vasoconstriction is affected as early as 50 years of age.
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