A New Approach to Retinal Oxygen Extraction Measurement Based on Laser Speckle Flowgraphy and Retinal Oximetry

Currently, no standard for the measurement of retinal oxygen extraction exists. Here, we present a novel approach for measurement of retinal oxygen extraction based on two commercially available devices, namely laser speckle flowgraphy (LSFG) and retinal oximetry. The study was conducted in a randomized, double-masked design. Two study days were scheduled for each healthy participant. On one study day, measurements were performed during breathing of 100% oxygen to induce hyperoxia and on the other study day during breathing of 12% oxygen in nitrogen to induce hypoxia. To obtain data for short- and long-term reproducibility, baseline measurements during breathing of room air were performed twice on both study days. Retinal oxygen extraction was calculated from retinal oxygen saturation measurements using the oxygen module of the dynamic vessel analyzer (Imedos, Jena, Germany) and retinal blood flow measurements using LSFG (Nidek, Tokyo, Japan). As expected, breathing of 100% oxygen induced a significant decrease in retinal oxygen extraction of 36% ± 17% (P < 0.001). During hypoxia, retinal oxygen extraction did not change from baseline (P = 0.153). For short-term reproducibility, the intraclass correlation coefficient was excellent (0.910) and good (0.879) for long-term reproducibility. Coefficient of variation between measurements was 9.8% ± 7.0% for short-term and 10.4% ± 8.8% for long-term reproducibility. The data obtained in the present experiments show that the new approach to measure retinal oxygen extraction is valid and reproducible in healthy volunteers. The technique may become a valuable tool in studying retinal hypoxia in a wide variety of ocular and systemic diseases in the future.