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GT Feke, LR Pasquale, JW McMeel; Retinal Hemodynamic Autoregulation During Postural Change . Invest. Ophthalmol. Vis. Sci. 2002;43(13):841.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose:We sought to characterize the retinal hemodynamic response to changes in posture in a group of healthy women in order to provide a database against which similar measurements in women with normal tension glaucoma could be compared. Methods:We used a Canon retinal laser Doppler blood flow instrument to measure the vessel diameter (D), the time variation of the blood speed (S(t)), the average blood speed (S), and the blood flow rate (F) at the same site in a major inferotemporal retinal artery of the left eye at baseline with the subjects seated, during a 30 minute period with subjects lying on their right side, and during the following 20 minute period with subjects once again seated. A Keller vital signs monitor was used to record the pulse rate and the systolic (BPs), diastolic (BPd), and mean brachial artery blood pressure (MAP) throughout the experiments. Retinal perfusion pressures (PP) were calculated according to the method of Hague and Hill (Br J Ophthalmol 1988;72:253-7). Six women, ages 40 to 60, mean age 48.7 years, were studied. Results:Baseline parameters (mean+/-sd) were BPs=12417 mmHg, BPd=7116 mmHg, MAP=9012mmHg, Pulse=7410 bpm, and IOP=133 mmHg. Final measurements while lying down were made after 303 minutes of recumbency. Final measurements while sitting were made 185 minutes after rising. While lying down, PP increased by 41.419.7%. In response to this increase, D decreased by 7.23.6% (p=0.03, One-Sample Sign Test), S increased by 19.55.4% (p=0.03), and F remained unchanged (2.89.0%) compared to baseline. After rising, PP was increased by 15.16.0% (p=0.03) compared to baseline. D (-1.22.0), S (1.316.5), and F (-1.117.3) were not significantly different from baseline. Conclusion:We have developed an experimental protocol that can be used as a physiological test of the capacity of the retinal circulation to maintain blood flow homeostasis in the face of large changes in perfusion pressure that are routinely encountered in daily life. We expect that our results will be useful when used for comparison with measurements in patients in whom vascular dysregulation may occur.
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