Oximetry of retinal vessels by dual-wavelength imaging: Calibration and influence of pigmentation

J. M. Beach*, K. J. Schwenzer, S. Srinivas, D. Kim, J. S. Tiedeman

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

231 Scopus citations


A method for noninvasive measurement of Hb O2 saturation (SO2) in retinal blood vessels by digital imaging was developed and tested. Images of vessels were recorded at O2-sensitive and O2-insensitive wavelengths (600 and 569 nm, respectively) by using a modified fundus camera with an image splitter coupled to an 18-bit digital camera. Retinal arterial SO2 was varied experimentally by having subjects breathe mixtures of O2 and N2 while systemic arterial SO2 was monitored with a pulse oximeter. Optical densities (ODs) of vascular segments were determined using a computer algorithm to track the path of reflected light intensity along vessels. During graded hypoxia the OD ratio (ODR = OD600/OD569) bore an inverse linear relationship to systemic SO2. Compensation for the influence of choroidal pigmentation significantly reduced variation in the arterial So2 measurements among subjects. An O2 sensitivity of 0.00504 ± 0.00029 (SE) ODR units/%SO2 was determined. Retinal venous SO2 at normoxia was 55 ± 3.38% (SE). Breathing 100% O2 increased venous SO2 by 19.2 ± 2.9%. This technique, when combined with blood flow studies in human subjects, will enable the study of retinal O2 utilization under experimental and various disease conditions.

Original languageEnglish (US)
Pages (from-to)748-758
Number of pages11
JournalJournal of applied physiology
Issue number2
StatePublished - Feb 1999


  • Hemoglobin oxygen saturation
  • Spectrophotometry

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)


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