A NEW METHOD FOR ASSESSMENT OF CHANGES IN RETINAL BLOOD-FLOW

This study validates the use of residence time distribution (RTD) func tions in human subjects to assess changes in retinal flow by using the widely recognized model of flow changes due to oxygen breathing. Chan ges in retinal blood pow may provide important Information for clinica l decisionmaking in several populations, including those with diabetic retinopathy, sickle cell disease and retinitis pigmentosa. Normal vol unteer subjects were studied before and after oxygen breathing After I V injection, relative fluorescence was obtained using scanning laser o phthalmoscopy/ image processing in all vessel branches (average, 17). For each experiment, 64 frames (2/s) were digitized and were normalize d using the RTD method. Vessel diameters were measured using densitome try techniques on fundus photos, where the diameter data made it possi ble to weight each vessel according to relative cross-sectional area t o obtain a true mean. circulation time (MCT). MCT increased for the gr oup of subjects when breathing oxygen compared to normal air (P=0.001) , representing a decrease in retinal blood flow. Average MCT increased 2.82+/-2.51 s for all subjects, with an increase of 2.93+/-2.26 s In repent trials for one subject. The proposed method uses information fr om all retinal vessels and allows the assessment of overall, as well a s selected, regional retinal flow. It is more comprehensive than previ ous methods analysing single vessel flow. This method will be potentia lly useful for assessing hemodynamic changes in the retina associated with a wide range of eye disease. (C) 1997 Elsevier Science Ltd for IP EM.