Visible-Light OCT Captures In-vivo Changes in Retinal Oximetry in Ischemic Retinal Diseases

Abstract

Purpose : Visible-light (vis-) OCT utilizes the hemoglobin light absorption properties within the visible spectral range to enable precise, in-vivo, non-invasive measurement of retinal oxygen saturation (sO²). This study tested the hypothesis that in ischemic retinal areas with neovascularization, the vein sO² is relatively lower compared to unaffected areas, to compensate for the impaired flow in the obstructed vessel.

Methods : The sO² was measured with our vis-OCT (8192 x 16 samplings in 1x1mm², horizontal sampling interval = 0.12 µm) prototype, in two matched artery and retinal veins, in the affected and unaffected areas, of 3 subjects with retinal vessel occlusion. Subject 1 - a 72 years old woman, 10 years after cilio-retinal branch occlusion; Subject 2 - a 38 years old woman, 5 months after central retinal vein occlusion (CRVO); and subject 3 - a 61 years old woman, 1.5 years after inferior branch retinal vein occlusion (BRVO). In order to get accurate sO² estimation, wavelength-dependent OCT amplitudes from identical depth locations across multiple A-lines were averaged. The averaged signal, based on Beer-Lambert’s law, was then fitted to hemoglobin absorption values.

Results : The retinal vein sO² in ischemic areas was consistently lower compared to veins in unaffected areas, with an average decrease of 6.3% (Table). The biggest difference was detected in the subject with BRVO while the smallest in the cilio-retinal branch occlusion. No difference was noted in retinal arteries sO².

Conclusions : The relative lower oxygen saturation in retinal veins located in ischemic areas with neovascularization might be due to an increase in oxygen consumption per unit volume of blood. Further studies are warranted to examine the diagnostic and monitoring use of oximetry information acquired with vis-OCT.

This is a 2020 Imaging in the Eye Conference abstract.

 

Table. sO² values in Ischemic and unaffected area