Analysis of retinal vasodilation after flicker light stimulation in relation to vasospastic propensity

PURPOSE. To explore the maximum retinal vasodilation in response to repeated flicker light stimulation in relation to vasospastic propensity in healthy subjects. METHODS. Twenty-four young healthy women were grouped as vasospastic and nonvasospastic, based on their history of cold extremities and on the results of nailfold capillaroscopy. A retinal vessel analyzer was used to obtain recordings of the ocular fundus during still illumination and three flicker light stimulations. Retinal vessels were analyzed in the immediate vicinity of the optic nerve head and 2 to 3 disc diameters away from the disc. The maximum dilatory amplitudes were always the highest 1-second mean vessel diameter in response to each of the three flicker light stimuli. RESULTS. Maximum dilatory amplitude ( in percent) was, in the proximal measurement site in the arterioles, 6.2 +/- 2.6, 4.8 +/- 2.1, and 6.6 +/- 3.9 in the vasospastic group, and 7.9 +/- 3.2, 8.6 +/- 4.1, and 9.1 +/- 4.7 in the nonvasospastic group in three repeated flicker stimulations. Corresponding values for distal measurement sites were 6.7 +/- 2.5, 4.8 +/- 3.4, and 4.7 +/- 4.4 and 9.0 +/- 3.7, 11.0 +/- 5.2, and 12.3 +/- 7.7. The maximum amplitude was significantly lower in the vasospastic group ( P = 0.001). The maximum venule dilation was also significantly lower in the vasospastic group ( P = 0.037). Vessel diameters failed to stabilize at the original baseline level during the 80-second recovery period, and this baseline offset had opposite signs in the arterioles in the vasospastic ( remained below the original baseline) and nonvasospastic ( remained above the original baseline) groups. CONCLUSIONS. The maximum dilatory amplitude was significantly lower in vessels in the vasospastic group. An augmentation of the maximum vasodilation was observed in the nonvasospastic group after repeated flicker stimulations, a phenomenon that was missing in arterioles of vasospastic subjects. It seems that such different behavior is due to the opposite baseline offsets in interflicker periods in the two groups.