Remote sensing of blood oxygenation using red-eye pupil reflection

Choudhary, T. R., Ball, D., Ramos, J. F., Stefansson, E. and Harvey, A. R. (2019) Remote sensing of blood oxygenation using red-eye pupil reflection. Physiological Measurement, 40(12), 12NT01. (doi: 10.1088/1361-6579/ab5f3b) (PMID:31805541)

Abstract

Objective: To develop a technique for remote sensing of systemic blood oxygenation using red-eye pupil reflection. Approach: The ratio of the intensities of light from the bright pupil reflections at oxygen sensitive and isosbestic wavelengths is shown to be sensitive to the oxygenation of blood in the eye. A conventional retinal camera, fitted with an image-replicating imaging spectrometer, was used at standoff range to record snapshot spectral images of the face and eyes at eight different wavelengths. In our pilot study we measured optical-density ratios (ODRs) of pupil reflections at wavelengths of 780 nm and 800 nm, simultaneous with pulse oximetry, for ten healthy human subjects under conditions of normoxia and mild hypoxia (15% oxygen). The low absorption at these infrared wavelengths localises the sensing to the choroid. We propose that this can be used for as a proxy for systemic oximetry. Main results: A significant reduction (P  <  0.001) in ODR of the pupil images was observed during hypoxia and returned to baseline on resumption of normoxia. We demonstrate that measurement of the choroidal ODR can be used to detect changes in blood oxygenation that correlate positively with pulse oximetry and with a noise-equivalent oximetry precision of 0.5%. Significance: We describe a new method to remotely and non-invasively sense the oxygen saturation of choroidal blood. The methodology provides a proxy for remote sensing of cerebral and systemic blood oxygenation. We demonstrate the technique at short range but it has potential for systemic oximetry at large standoff ranges.

• Item Type: Articles
• Keywords: Choroid, oximetry, remote sensing, spectral imaging.
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Harvey, Professor Andy
• Authors: Choudhary, T. R., Ball, D., Ramos, J. F., Stefansson, E., and Harvey, A. R.
• College/School: College of Science and Engineering > School of Physics and Astronomy
• Journal Name: Physiological Measurement
• Publisher: IOP Publishing
• ISSN: 0967-3334
• ISSN (Online): 1361-6579
• Published Online: 05 December 2019
• Copyright Holders: Copyright © 2019 Institute of Physics and Engineering in Medicine
• First Published: First published in Physiological Measurement 40(12): 12NT01
• Publisher Policy: Reproduced in accordance with the publisher copyright policy