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Keiko Yamada, Brendan Seto, Christopher Llerena, Christopher Hsu, Chie Sotozono, Takatoshi Maeno, Jorge G Arroyo; The effect of hyperoxia and hypercapnia on retinal vascular blood flow in healthy adults. Invest. Ophthalmol. Vis. Sci. 2019;60(9):5742.
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We used two non-invasive imaging devices including spectral domain optical coherence tomography (SD-OC) and laser-speckle flowgraphy (LSFG) to measure retinal arteriolar vasoreactivity using both normobaric hyperoxia and hypercapnia.
Imaging consisted of optic nerve head photography under the tracking mode of SD-OCT (Heidelberg Spectoralis, Heidelberg Engineering, Germany) and retinal vascular imaging using the LSFG (LSFG-NAVI, SoftCare, Fukuoka, Japan). Subject initially sat for 15 minutes before taking baseline retinal images. They then inhaled CO2 rich air for 3 minutes before and during follow-up retinal images. After breathing room air for 15 minutes, subjects inhaled 12 L/min of Oxygen for 15 minutes using a facemask before taking a final set of images. In order to include both usual exhalation and inspiration periods, each measurement was performed three times while maintaining a respiratory rate constant at approximately one breath every 5 seconds.
This study studied eighteen retinal arteries (RA) of 2 male and 1 female non-smoking healthy volunteers (mean age: 47±9 years old). The mean RA diameters at baseline was 132.69±20.28 μm and did not vary significantly by subject (F = 1.25, p = 0.31). The changes in diameter from baseline to hypercapnia (mCO2 / Air = 1.08, p < 0.05) and baseline to hyperoxia (mO2 / Air = 0.912, p < 0.05) were statistically significant.
Hypercapnia and hyperoxia had an opposite effect on retinal vasoreactivity. This change in vessel diameter may have an effect on vessel blood flow and oxygenation. Further research should examine the difference between retinal arterial dilation and constriction in patients with a variety of retinal conditions.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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