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Oxygen saturation in retinal blood vessels increases in the dark
Invest Ophthalmol Vis Sci. 2009;50(5):2308-2311.
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Oxygen saturation in retinal blood vessels was higher in dark conditions than in light conditions, according to a study.
“Our study shows for the first time the change in human retinal oxygen metabolism in light and dark,” the study authors said. “These changes may be vital to our understanding of retinal oxygen metabolism in health and in ischemic eye diseases, such as diabetic retinopathy.”
Investigators used a retinal oximeter, which comprises a fundus camera coupled with a beam splitter and digital camera, to gauge hemoglobin oxygen saturation in the retinal blood vessels.
The study comprised two experiments. In the first experiment, 18 subjects underwent oximetry measurements after 30 minutes in the dark, followed by 5-minute intervals of white light and dark. Three subjects were excluded because of poor image quality.
In the second experiment, 23 subjects underwent oximetry after 30 minutes in the dark, followed by 5-minute periods of low, medium and bright light, and an additional 5 minutes of dark. Four subjects were excluded.
Results of the first experiment showed oxygen saturation diminishing from 92% after 30 minutes in the dark to 89% after 5 minutes in light (P = .008). Data from the second experiment showed oxygen saturation decreasing from 92% in the dark to 88% in bright light (P = .012).