Abstract
PURPOSE: The Bayliss effect describes the reaction of smooth muscle cells in the
arterial wall to changes in blood pressure. A rise in mean arterial blood
pressure (MAP) causes an autoregulatory myogenic vessel constriction by smooth
muscle cells in the arterial wall. The responsiveness of retinal vessels to
changes in MAP were analyzed using the Retinal Vessel Analyzer (RVA). METHODS:
Continuous measurement of retinal arterial vessels was performed in 40 healthy
volunteers (age 18-56 years.) over a 9-min period. After a 3-min baseline
measurement (phase I), isometric exercise caused a rise in MAP over the next 3
min (phase II). During the last 3 min (phase III) recovery was observed. Blood
pressure and ECG were documented simultaneously throughout the experiment.
RESULTS: Exercise caused a significant rise of 22.8 (+/-6.0) mm Hg in MAP (phase
II vs. phase I: P<0.001). Retinal arterioles showed 5.5\% (+/-2.8\%)
vasoconstriction (P<0.001). During phase III vessel diameters returned to normal,
with no difference from phase I (P = 0.179). CONCLUSION: Noninvasive measurement
and quantitative analysis of the Bayliss effect in human retinal vessels by means
of the RVA is possible. Analysis of retinal arterial autoregulation may provide
valuable insight into pathologic conditions such as diabetic or hypertensive
retinopathy.
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