NO. 2 Original Contributions Retinal Vascular Autoregulation in Normal Subjects

SUMMARY The retinal arterial diameter and its response to changes in perfusion pressure were measured by means of a fundus camera in 65 normal subjects. A reduction of effective MABP was induced by a postural change from a recumbent to an erect position. A small but significant increase in retinal arterial diameter was observed by reduction of the perfusion pressure in all subjects. The reduction of retinal arterial reactivity in response to blood pressure changes (- % change in diameter/A effective MABP) was significantly correlated with advancing age (p < 0.01). No significant correlations were observed between the retinal arterial reactivity, magnitude of the retinal arterial diameter (range: 60-140 n), and systemic blood pressure (range of MABP: 75-110 mmHg). These results indicate that the retinal artery has an autoregulatory mechanism which is influenced by aging. Stroke, Vol 13, No 2, 1982 CEREBROVASCULAR AUTOREGULATION is defined as constancy of blood flow despite changes in perfusion pressure within the range of 50-160 mmHg.1,2 The mechanism of autoregulation is mediated by changes in arterial calibre; the vessel