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Adam M Dubis, Luke Nicholson, Roxanne Crosby-Nwaobi, Phil Hykin, Sobha Sivaprasad; Retinal morphology and vessel oxygen saturation in normal and diabetic patients. Invest. Ophthalmol. Vis. Sci. 2017;58(8):3033.
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© ARVO (1962-2015); The Authors (2016-present)
Sufficient capillary flow and dispersion of oxygenated blood is required for the maintenance of all tissue, with disruptions leading to disease. There is a gap in our understanding of how diabetic eye disease affects retinal oxygenation. Current analysis schemes are time consuming and do not provide comprehensive analysis of retinal oxygenation. There is a need to develop better analysis tools for understanding how oxygen saturation changes between normal and diabetic state. This knowledge is essentially for better treatment planning and prediction of therapeutic success.
Fourteen controls and twenty-one subjects with diabetes but without areas of non-perfusion were recruited for this prospective study. Subjects were imaged using SDOCT and Oxymap T1 retinal oximeter. Normal subjects were imaged twice, roughly 30 minutes apart to assess repeatability. For oxygen saturation measurements, image size was 35deg and centered at the optic nerve. Vessel size, location and saturation were exported using instrument software and analysed using custom Matlab software. Offline analysis separated arteriole and venule derived signals and assessed global oxygenation saturation, saturation by distance from the optic nerve, saturation by vessel diameter.
Agreement between multiple measures of global saturation was +0.33% (-9.5 to 10.1% 95% confidence interval) for arteriole and -0.9% (-12.3 to 10.5% 95% confidence interval). There was no difference in global arteriole oxygen saturation, 91.6% in normal and 89.5% in diabetics, however there was a significant difference in venule saturation (63.7% verse 55.6%, p = 0.0219). The difference between arteriole and venule oxygen saturation was seen in the larger vessels; 100-120um (36.3 vs 42.1%; p = 0.045) and 120-140um (37.5 vs 45.2%; p = 0.032). The difference was due to venule saturation being higher in the diabetics than normal controls in larger vessels.
These data suggest that even without areas of non-perfusion, there is a fundamental change in retinal oxygen dispersion. The new tools developed here provide a more comprehensive analysis. The new data suggests that the lack of difference in small verse large vessel is probably an artefact of the greater pooling of blood in large vessels near the optic nerve. To further understand these changes, instrumentation to understand blood flow and oxygen dispersion in the capillaries is needed.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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