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P.A. Rose, C. Hudson; Comparison of Retinal Arteriolar and Venular Responses to Isocapnic Hyperoxia in Healthy Subjects . Invest. Ophthalmol. Vis. Sci. 2005;46(13):3910.
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Purpose: To compare the magnitude and variability of blood flow measurements acquired from retinal arterioles and venules. Measurements were collected using the Canon Laser Blood Flowmeter (CLBF) model 100, a laser Doppler instrument that permits the quantitative, noninvasive measurement of retinal blood velocity and vessel diameter to derive blood flow. Methods: CLBF measurements were collected from 11 healthy subjects (mean age 26.8 yr; range 22–36 yr; 5M:6F) before, during and after exposure to hyperoxia, a provocation known to constrict blood vessels and reduce blood velocity and flow. Isocapnia was maintained using a previously validated sequential rebreathing circuit. Blood pressure, heart rate, respiration rate, and inspired and expired oxygen and carbon dioxide levels were monitored throughout the study using a Datex critical care monitor. Results: Hyperoxia resulted in significant decreases in superior temporal retinal arteriolar and venular blood velocity (35%, p<0.050; 28%, p<0.001, respectively) and flow (47%, p<0.05; 48%, p<0.01 respectively). Arteriolar diameter decreased by 10% and venular diameter by 15% (not significant). The coefficients of variation (CV = SD/mean) for intra–individual arteriolar and venular measurements were similar. None of the subjects’ vital signs changed significantly in response to the hyperoxic provocation. Conclusions: The magnitude and intra–subject variability of retinal arteriolar and venular responses to hyperoxia were similar. Thus, measurements taken in either type of vessel are similarly representative of changes in retinal blood flow.
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