Oxygen saturation measurements of retinal arteries and veins during physiologic changes

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Purpose. The development of an instrument to noninvasively measure the oxygen saturation of blood within retinal arteries and veins, and the characterization of retinal saturation variations during physiologic changes. Methods. A prototype Eye Oximeter (EOX) has been completed that shines low-power diode lasers into the eye and scans them across the large vessels of the retina. The reflected light intensities are digitized via 14-bit A/D, and transferred to a 486-based PC for analysis. Curve fitting techniques compensate for vessel specular reflections, and determine the percent absorption of the blood. Oxygen saturation is calculated from the measured absorptions at multiple wavelengths. A complete saturation measurement is made by averaging 8 scans occurring in less than one second. The EOX was used in a pilot study with anesthetized swine. Arterial measurements made during graded hypoxia provide in vivo calibration of the EOX. Retinal venous saturation (SrO2) was correlated with mixed venous saturation (Sv̄O2) as 20% of total blood volume was removed over 40 minutes. Results. We measured a strong correlation (r 2=0.96±0.03) between retinal arterial saturation and femoral artery blood gas measurements during graded hypoxia. During exsanguination, we measured a strong correlation (r2=0.86±0.09) between SrO2 and Sv̄O2. Conclusions. Due to the strong correlation between SrO2 and Sv̄O2 during blood loss, the EOX could provide a portable, noninvasive technique for early monitoring of occult bleeding.

Original languageEnglish (US)
Pages (from-to)S840
JournalInvestigative Ophthalmology and Visual Science
Issue number3
StatePublished - Feb 15 1996

ASJC Scopus subject areas

  • Ophthalmology
  • Sensory Systems
  • Cellular and Molecular Neuroscience


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