Abstract
We measured hemoglobin oxygen saturation (sO2) in the retinal circulation in healthy humans using visible-light optical coherence tomography (vis-OCT). The measurements showed clear oxygenation differences between central retinal arteries and veins close to the optic nerve head. Spatial variations at different vascular branching levels were also revealed. In addition, we presented theoretical and experimental results to establish that noises in OCT intensity followed Rice distribution. We used this knowledge to retrieve unbiased estimation of true OCT intensity to improve the accuracy of vis-OCT oximetry, which had inherently lower signal-to-nose ratio from human eyes due to safety and comfort limitations. We demonstrated that the new statistical-fitting sampling strategy could reduce the estimation error in sO2 by three percentage points (pp). The presented work aims to provide a foundation for using vis-OCT to achieve accurate retinal oximetry in clinical settings.
Highlights
Retinal oxygen metabolism is a key factor in the pathogenesis of leading blinding diseases, including diabetic retinopathy (DR) and age related macular degeneration (AMD) [1,2,3,4]
3.1 Statistical sampling can reduce oximetry estimation error To demonstrate how the aforementioned statistical sampling approach benefit visible-light optical coherence tomography (vis-OCT) oximetry, we carried out the following numerical simulation
We showed vis-OCT results from four healthy volunteers of both genders with an age span from 20s to 60s
Summary
Retinal oxygen metabolism is a key factor in the pathogenesis of leading blinding diseases, including diabetic retinopathy (DR) and age related macular degeneration (AMD) [1,2,3,4]. Retinal metabolic rate of oxygen (rMRO2), a hallmark of retinal metabolism, may be a key biomarker for early disease screening, evaluating disease severity, and monitoring response to therapeutic intervention. Retinal blood flow and retinal oxygenation, are required to quantify rMRO2. Retinal blood flow can be calculated given the diameter of retinal blood vessels and their flow velocity, both of which can be reliably quantified using the state-of-the-art ophthalmic imaging tools [9,10,11]. The major challenge that hinders the incorporation of rMRO2 into ophthalmic care is the lack of a well-established method for accurate retinal oxygen measurement in clinics
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