Measurement of autoregulation of retinal blood flow using the blue field entoptic phenomenon

Autoregulation of retinal blood flow was studied in seven normal volunteers. The stimuli to autoregulation used were hyperoxia and hypoxia under controlled conditions of isocapnia. Macular blood flow was measured using the blue field entoptic phenomenon and retinal artery and vein diameters were measured using a computerised digitising system. Results under conditions of isocapnic hypoxia showed a 38 per cent average increase in blood flow and an increase in diameter of 8.2 per cent and 7.4 per cent in retinal arteries and veins respectively. In hyperoxia blood flow fell by an average of 36 per cent and retinal artery and vein diameter decreased by 5.6 per cent and 10 per cent respectively.