A new approach for measuring retinal oxygen extraction based on laser speckle flowgraphy and retinal oximetry

Abstract

Purpose : It has been found that several ocular diseases are associated with reduced retinal oxygen metabolism. Measurement of retinal oxygen extraction is, however, time consuming and mostly based on custom-built devices. The aim of the present study was to assess the feasibility of a new approach for measuring retinal oxygen extraction based on two commercially available devices, namely laser speckle flowmetry (LSFG) and retinal oximetry.

Methods : Ten healthy subjects participated in the present study. Total retinal blood flow (TRBF) was assessed by measuring retinal blood flow in every vessel around the optic nerve head by LSFG. At the same vessel position, retinal oxygen saturation was measured and out of these parameters corrected arterial (cO_2,CRA) and venous (cO_2,CRV) oxygen content was estimated and the difference between these two parameters (cO_2,DIFF) was determined. Using TRBF and cO_2,DIFF it was then possible to calculate retinal oxygen extraction. To validate the approach, measurements were performed at baseline and during breathing of 100% oxygen, as it is well known that retinal oxygen extraction decreases during hyperoxia.

Results : As expected, TFBF significantly decreased during 100% oxygen breathing (-14±15%, p=0.016). While cO_2,CRA only slightly increased by 1±2% (p=0.093), cO_2,CRV increased by 9±14% (p=0.050). Consequently, cO_2,DIFF decreased by 10±20% (p=0.087). This led to a pronounced decrease in retinal oxygen extraction by -21±30% during hyperoxia (p=0.020).

Conclusions : During hyperoxia, a significant decrease in TRBF and retinal oxygen extraction as measured by combining LSFG and retinal oximetry measurements was observed, which is in accordance with previous findings in the literature and physiologically expected. Therefore, the presented approach for measurement of retinal oxygen extraction seems feasible. Larger studies in patient cohorts using this method should be conducted in the future.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.