Retinal Oximetry and blood flow

Summary The retina has highest metabolic demand compared to any other tissue in the human body and regulation of the retinal blood flow, blood oxygen saturation (SO 2 ) and thereby oxygen delivery (DO 2 ) are crucial to preserve vision and function. The study reports inner retinal DO 2 and consumption (VO 2 ) during controlled and stable normoxia, hyperoxia and hypoxia in humans. Eleven subjects underwent measurement of total retinal blood flow (TRBF) and retinal blood oxygen saturation (SO 2 ) using prototype methodologies of Doppler Spectral Domain Optical Coherence Tomography and Metabolic Hyperspectral Camera, respectively. TRBF decreased significantly (p = 0.010) from 43.17  μ l/min (+12.7) to 36.23  μ l/min (+4.6) during hyperoxia, conversely, TRBF increased significantly (p < 0.008) to 52.89  μ l/min (+10.9) from baseline during hypoxia. The average inner retinal O 2 delivery during normoxia was 8.48 mlO 2 /100 g/min and inner retinal consumption was 3.64 mlO 2 /100 g/min and these values changed during provocation to maintain a stable DO 2 and VO 2 . Change in TRBF and SO 2 reflect metabolic autoregulatory function of the retinal tissue indicating that retinal blood flow and SO 2 are able to precisely compensate for changes in inspired oxygen.