Purchase this article with an account.
W Vilser, E Nagel, S Kremmer; Autoregulative Capacity of Retinal Blood Flow Estimated by Means of RVA-Measurements and Model Considerations . Invest. Ophthalmol. Vis. Sci. 2002;43(13):3295.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Purpose: To estimate the meaning and autoregulative capacity (AC) of changes in arterial and venous vessel diameter for the control of retinal blood flow. Vessels are the essential adjusting units of autoregulation by dilating or constricting their diameter. We defined autoregulative capacity (AC) as the difference of the maximum and minimum of blood flow (ACF) or of retinal Perfusion Pressure (ACP) induced by provocation methods causing maximum vasodilation or constriction. Methods: Vasodilation was provoked by a short increase of intraocular pressure to suprasystolic values, constriction by means of 5 min 100% oxygen breathing. Vessel diameter was measured continuously before, during and after provocation by means of RVA (Retinal Vessel Analyzer of IMEDOS GmbH, Germany). Maximum of dilation and constriction were assessed at arteria and vena temp. sup. or inf. for both provocation groups in 12 and 10 healthy subjects (mean age: 37.4 and 33.4 years). The AC was calculated by means of a retinal microcirculation network and flow model of a retinal quadrant based on nonlinear Casson flow relation. Measuring results and model parameters of a healthy subject with average values were used for input of model simulations. Results: Mean maximum of dilation: arterial +7.0 % , venous 9.3 % and of constriction: arterial:-5.6% , venous: -13.0%. The calculated AC amount from -22.7 to +25.0% for ACF and from -11.9 to +28.5 mmHg for ACP in relation to baseline diameters. Conclusion: Assuming that the measured values are the limits of possible autoregulative changes for arterial and venous diameters, then the retinal autoregulation can compensate for changes in retinal blood pressure or intraocular pressure in a range of about 40.4 mmHg. Functional tissue demand can only change vessel diameters which are responsable for blood flow changes within 47.7%. In relation to measurable changes in systemic or retinal blood pressure and intraocular pressure these results can be of interest for the detection of individual vascular causes in glaucoma.
This PDF is available to Subscribers Only