Retinal vessel analysis and oximetry ‐ technical advances and clinical applications

Purpose To develop and evaluate a method for simultaneous measurements of retinal vessel oxygen saturation and vessel diameter change upon flicker light stimulation. Methods Dual – wavelength (548 nm and 610 nm) fundus images were taken before (baseline) and during luminance flicker stimulation (12.5 Hz, modulation depth: 1:25). Retinal vessel oxygen saturation (OS, dual – wavelength optical oximetry) and diameters (central retinal arterial and venous equivalents – CRAE and CRVE) were determined. Investigations were performed in 19 healthy volunteers (mean age: 26 ± 2.5 years), 18 patients with diabetic retinopathy (62.2±8.3 years), 16 glaucoma patients with IOP (≤22 mmHg, mean 16±3.5 mmHg, mean age 66±14 year), and 20 age matched controls (71.2±7.5 years). Results In the young population, the flicker increased CRAE, CRVE, and venous OS statistically significant from 193 ± 20 µm, 228 ± 20 µm, and 60 ± 5.7% at baseline to 202 ± 19 µm, 242 ± 17 µm, and64 ± 5.9% (all p<0.0005).. Flicker light increased CRAE, CRVE, and venous OS by 1.42%±3.72%, 2.80%*±2.70%, and 2.03%*±2.43% in the patients as well as 4.98%*±6.23%, 8.94%*±5.26%, and 4.20%*±3.71% in the controls (*: p<0.05). Also in glaucoma patients, the increase of venous OS upon flicker was smaller in the patients than in the controls (1.9±4.9%). Conclusion Oxygen supply or consumption is reduced in diabetic retinopathy as well as glaucoma. The simultaneous measurements of retinal vessel oxygen saturation and vessel diameter change upon flicker light stimulation should be considered for the investigation of such impairment of oxygen supply.Commercial interest