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Randy Kardon, Cole Starkey, Jan M Full, Anna Ketcham, Brian Tong, Gary Pierce, Seth Holwerda, Jess Fiedorowicz; Human Retinal Vascular Reactivity to Flickering Light and Cold Water Immersion Measured by Laser Speckle Flowgraphy. Invest. Ophthalmol. Vis. Sci. 2017;58(8):3043.
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© ARVO (1962-2015); The Authors (2016-present)
We performed a prospective analysis of retinal blood flow, ocular perfusion pressure and changes in vascular resistance in response to stimuli in humans. We sought to understand the dynamics of vascular reactivity in response to two external stimuli: flickering light and hand immersion in ice water.
12 normal subjects (6 male and 6 female, mean age=31; range 24-44) underwent laser speckle flowgraphy (LSFG-NAVI; Softcare LTD, Fukuoka, Japan) in the left eye following mydriasis with tropicamide 0.5%. Baseline flow measurements over 4 heartbeats were recorded in a retinal region of interest of approximately 15 x 10 degrees, including the optic nerve and fovea. Following baseline blood flow measurements, a 10Hz flickering light stimulus with 50% duty cycle and intensity of 14,600 cd/m2 was given for 2 minutes while recording flow and blood pressure at 30, 60, 90, and 120 seconds during and after the stimulus. The same sequence of measurements was also made during and after immersing the left hand into ice water.
A light-evoked increase in retinal blood flow occurred at onset of light flicker and peaked at 90 seconds (mean=20%±14 increase; minimum 4%, maximum 44%). A parallel reduction in vascular resistance occurred (mean=14%±10; minimum 0%, maximum 29%). Cold-water hand immersion caused an increase in retinal blood flow peaking at 90 seconds (mean=15%±14; minimum 18% decrease, maximum 44% increase) with a concomitant rise in perfusion pressure. Vascular resistance increased (mean=18%±11, minimum 17% decrease, maximum 35% increase).
A flickering light caused an increase in blood flow and decrease in vascular resistance, representing a metabolic stress test. Cold-water caused an increase in retinal blood flow, but an increase in vascular resistance, associated with a rise in mean arterial blood pressure and ocular perfusion pressure. Cold-water immersion represents a sympathomimetic stimulus with corresponding autoregulation of retinal blood flow, resulting in vasoconstriction. These two stress tests may be useful for characterizing vascular reactivity in healthy and diseased states.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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