On Pulse-Wave Propagation in the Ocular Circulation

Abstract

PURPOSE: To measure the oscillation phase delay between retinal arterioles and venules in order to analyze pulse wave propagation in the ocular circulation of vasospastic and nonvasospastic subjects and a change thereof during the cold pressor test in another group of healthy subjects. METHODS: Twenty-four young, healthy women, 12 vasospastic and 12 nonvasospastic, were analyzed. A retinal vessel analyzer was used to obtain 1-minute recordings of the ocular fundus. A phase delay between the arteriole and venule pulsations was assessed at three sites, one (proximal) in the close retinal vicinity of the disc, one (middle) 1 to 2 disc diameters away from the disc, and a third (distal) 3 to 4 disc diameters away from the disc; and, assuming that venules are counterphased to the choroidal circulation, a choroid-to-retina pulse delay was calculated. In addition, the change in these parameters was analyzed during the modified cold-pressor test in 10 healthy subjects (five women, five men). RESULTS: Pulse oscillations in arterioles led those in venules by 95.0 degrees +/- 39.0 degrees , 60.5 degrees +/- 57.5 degrees , and 47.5 degrees +/- 64.0 degrees in vasospastic subjects, and 76.0 degrees +/- 58.0 degrees , 31.5 degrees +/- 60.0 degrees , and 2.5 degrees +/- 80.5 degrees in nonvasospastic subjects in the proximal, middle, and distal measuring sites, respectively. Calculated choroid-to-retina pulse delays in vasospastic subjects were 0.20 +/- 0.10, 0.28 +/- 0.14, and 0.30 +/- 0.11 seconds and in nonvasospastic subjects 0.25 +/- 0.15, 0.35 +/- 0.11, and 0.43 +/- 0.2 seconds at the proximal, middle, and distal measuring sites, respectively. The difference was significant between vasospastic and nonvasospastic subjects (P = 0.033) and among the measuring sites (P = 0.0023). During exposure to cold, the choroid-to-retina pulse delays changed from 0.31 +/- 0.08, 0.40 +/- 0.16, and 0.51 +/- 0.26 seconds to 0.26 +/- 0.12, 0.30 +/- 0.10, and 0.33 +/- 0.14 seconds at the proximal, middle, and distal measuring sites, respectively (P = 0.024 for the change from baseline to cold exposure, and P = 0.022 for measuring sites). CONCLUSIONS: Retinal vessels in vasospastic subjects demonstrate an altered pattern of oscillation phase delay between arterioles and venules. Vessels in vasospastic subjects seem to conduct pulse waves faster and are thus stiffer than those in nonvasospastic subjects. The pattern of oscillation demonstrates changes during the cold pressor test in healthy subjects, indicating faster pulse-wave propagation.