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Jona Kristjansdottir, Sveinn Hardarson, Gisli Halldorsson, Robert Karlsson, Thorunn Eliasdottir, Einar Stefánsson; Retinal Oximetry with Scanning Laser Ophthalmoscope. Invest. Ophthalmol. Vis. Sci. 2013;54(15):44.
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© ARVO (1962-2015); The Authors (2016-present)
To test the sensitivity of a scanning laser ophthalmoscope for measurements of hemoglobin oxygen saturation in retinal blood vessels.
Fundus images were acquired with a scanning laser ophthalmoscope, Optomap 200Tx (Optos plc.). The device uses two wavelengths for image acquisition, 532 and 633 nm. Images taken at both wavelengths were analyzed with the Oxymap Analyzer software (Oxymap ehf.), which automatically tracks retinal vessels and calculates optical density ratio (ODR) between wavelengths for the vessels. ODR is inversely related to oxygen saturation. Two different methods were used to investigate the sensitivity of the device, oxygen inhalation and measurements of patients with central retinal vein occlusion, where hypoxia has been confirmed with Oxymap T1 oximeter. Two healthy subjects were measured after inhalation of pure oxygen for 10 minutes (10L/min) and every 5 seconds for the next 135 seconds, during recovery. Three patients with central retinal vein occlusion (CRVO) and one patient with hemi-central retinal vein occlusion were measured.
The figure shows results from the oxygen inhalation testing and the table shows oxygen saturation (mean±standard deviation) from CRVO patients, affected eye and fellow eye.
The Optomap 200Tx, scanning laser ophthalmoscope is sensitive to changes in oxygen saturation, but the variability between measurements is considerable as indicated by high standard deviation of saturation measurements. Further technical improvement is needed for optimization of measurements.
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