RETINAL HEMODYNAMICS IN MIDDLE-AGED NORMAL SUBJECTS

The laser Doppler technique and monochromatic photography were used to measure the total retinal blood flow, temporal/nasal differences in b lood flow and the relationship between blood flow and vessel diameter in 5 healthy subjects, aged 54-58 years. Systemic blood pressure (BP) and intraocular pressure were also measured, and the retinal perfusion pressure was calculated. The measurements were compared to those prev iously obtained from a younger group of 7 healthy subjects, aged 25-38 years. Total retinal blood flow was 73 +/- 13 mu l/min in the middle- aged subjects and was not significantly different from the value measu red in young subjects (80 +/- 12 mu l/min). Retinal perfusion pressure was significantly higher in the older subjects, primarily due to elev ated systemic BP. The similarity in total flow between the two groups, even though the retinal perfusion pressures were higher in the older group, is an indication of an increased vascular resistance to flow. T he increase may be an aging phenomenon or an indication of a well-func tioning autoregulatory capacity in the retinal vasculature of the olde r subjects.