Abstract
The purpose of the present study was to investigate the possibility to estimate CBF autoregulation by the retinal vascular responsiveness to changes in perfusion pressure.
The retinal arterial diameter and its response to changes in blood pressure were measured by means of a fundus camera in 46 control subjects and in 26 patients with cerebrovascular disease (CVD), 7 with Parkinson's disease and 1 with Shy-Drager syndrome.
Reduction of effective mean arterial blood pressure was induced by the postural change from a supine to an erect position.
Changes in diameter of the retinal vessel were quantitatively analysed by the use of Retinal Vasomotor Index (RVI) [-a change in diameter (%) /a change in effective mean arterial blood pressure (mmHg)].
The results obtained are summarized as follows :
1) RVI in control subjects showed no significant differences between male and female or between right and left eye. The reduction of RVI correlated with advancing age (r=-0.299, P<0.01).
2) RVI in patients with Parkinson's disease was significantly lower when compared with that in control subjects (p<0.005). In a patient with Shy-Drager syndrome, there was no significant response of the vessels to the fall in perfusion pressure.
3) RVI in cases with supratentorial infarction, infratentorial infarction, intracerebral hemorrhage and vertebrobasilar insufficiency was all significantly lower than that in control subjects (p<0.001, p<0.02, p<0.05, and p<0.01, respectively). In cases with unilateral supratentorial infarction, there was no significant difference in RVI between affected and non-affected side of the lesion. RVI in each side was lower than that in control subjects (p<0.001 and p<0.001, respectively).
4) RVI in cases without orthostatic hypotension was significantly higher than that in cases with orthostatic hypotension (p<0.01).
Present data indicate that autonomic nervous system play a role in the mechanism of autoregulation of retinal blood flow and are compatible with previous data of CBF autoregulation. It is concluded that the observation of the retnial blood flow autoregulation is a useful and non-invasive method to estimate the CBF autoregulation.
