A novel approach for measurement of retinal oxygen extraction based on laser speckle flowgraphy and retinal oximetry

Abstract

Aims/Purpose: Several ocular diseases lead to a reduction in retinal oxygen metabolism. However, measurement of retinal oxygen extraction is mostly based on time‐consuming and custom‐built devices. Hence, the aim of this study is to assess retinal oxygen extraction based on measurement of retinal blood flow with the commercially available laser‐speckle flowgraphy (LSFG) and measurement of retinal oxygen saturation with the commercially available retinal oximetry.Methods: Ten young healthy subjects participated in the present study. Retinal blood flow and retinal oxygen saturation were measured in each vessel around the optic disc at the same position. The corrected arterial (co2, CRA) and venous (co2, CRV) oxygen content was estimated from the parameters evaluated and the difference between these two determined parameters (co2, DIFF) was assessed. Retinal oxygen extraction was calculated using mean vessel flow rate (MV) and cO2, DIFF. To validate the novel approach, baseline measurement and measurement during inhalation of 100% oxygen were performed, as retinal oxygen extraction is known to decrease during hyperoxia.Results: MV significantly decreased during 100% oxygen breathing (−23 ± 10%, p < 0.001). While cO2, CRA only slightly increased by 1 ± 2% (p = 0.093), cO2, CRV increased by 9 ± 14% (p = 0.050). Consequently, cO2, DIFF decreased by 10 ± 20% (p = 0.087). This led to a pronounced decrease in retinal oxygen extraction by −31 ± 18% during hyperoxia (p < 0.001).Conclusions: During breathing of 100% oxygen a significant decrease in TRBF and retinal oxygen extraction was assessed. The decrease in retinal oxygen extraction during hyperoxia is consistent with findings in literature and is physiologically expected. Therefore, the novel approach for measurement of retinal oxygen extraction appears to be feasible. Larger studies in patient cohorts using this method should be conducted in the future.