Noninvasive Measurement of Oxygen Saturation in Human Retinal Blood Vessels and Tissues With Multispectral Confocal Imaging

BACKGROUND AND OBJECTIVE: Proof of concept for the first system of noninvasive human retinal vessel and tissue oxygenation measurement in axial and radial directions. MATERIALS AND METHODS: A confocal imaging system capable of calculating and mapping relative retinal blood oxygenation in radial and axial directions from three eyes of two healthy subjects was built. The relationship between oxygenation and retinal depth in vivo was analyzed to illustrate application of this novel system. RESULTS: The system shows capacity for measuring oxygenation along retinal depth for the first time. (1) Arteriovenous oxygenation difference decreases with blood vessel diameter. (2) Artery-tissue oxygenation difference is greater than vein-tissue oxygenation difference in the same region. (3) Intravascular-extravascular oxygenation difference decreases with blood vessel diameter. (4) Oxygenation data reported with a 95% CI are as follows: A1 91.5% +/- 18.2%, V1 32.8% +/- 18.6%, A2 97.3% +/- 17.8%, V2 64.4% +/- 11.2%, A3 73.2% +/- 19.1%, V3 52.9% +/- 15.3%, and Tissue 56.6% +/- 00.4%. CONCLUSION: This article demonstrates proof of concept for retinal oxygenation calculation in radial and axial dimensions for the first time. Initial results provide biological validity to this method. Future aims include further characterization of this system's results in healthy subjects and subsequent comparison of oxygenation between diseased and healthy retinae.