December 1986
Volume 27, Issue 12
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Articles  |   December 1986
Autoregulation of human retinal blood flow. An investigation with laser Doppler velocimetry.
Investigative Ophthalmology & Visual Science December 1986, Vol.27, 1706-1712. doi:
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      C E Riva, J E Grunwald, B L Petrig; Autoregulation of human retinal blood flow. An investigation with laser Doppler velocimetry.. Invest. Ophthalmol. Vis. Sci. 1986;27(12):1706-1712.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

The effect of acute changes in mean retinal perfusion pressure, P (2/3 of mean brachial artery blood pressure minus IOP), on retinal volumetric blood flow rate, Q, was investigated in normal volunteers. Changes in Q were determined from Q = k X Vmax X D2, where Vmax is the center line red blood cell velocity measured from temporal veins by laser Doppler velocimetry, D is the vessel diameter obtained by monochromatic fundus photography, and k is a constant of proportionality. A suction cup was used to induce step changes in IOP and, consequently, in P. The magnitude of the steps ranged from 10-32 mmHg. During the first 30 sec after a step decrease in P, Vmax and Q were significantly smaller than at rest by an amount proportional to the decrease in P. Thereafter, Vmax and Q increased markedly towards their values at rest, although P changed comparatively little during this period of time. Time constant of the corresponding decrease in vascular resistance, R(t) = P(t)/Q(t), was approximately 45 sec. There was no significant change in D during elevated IOP. Removal of the cup induced an immediate step increase in P, Vmax, D, Q, and R. Thereafter, Vmax, D, Q, and R returned to their values at rest (time constant of the change in R was about 30 sec), while P remained nearly constant. The rapid change in vascular resistance following a step decrease and increase in P can be attributed to an active process that attempts to maintain blood flow close to normal, in spite of changes in perfusion pressure (autoregulation).(ABSTRACT TRUNCATED AT 250 WORDS)

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