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Martin Hammer, Susanne Jentsch, Kia-Uwe Schmidtke, Sven Peters, Kai Wildner, Dietrich Schweitzer, Jens Dawczynski; Response of Retinal Vessel Diameters and Hemoglobin Oxygenation to Flicker Light Stimulation of Neuronal Activity in Glaucoma Patients. Invest. Ophthalmol. Vis. Sci. 2012;53(14):253.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate the response of retinal vessel diameters and oxygen saturation to flicker light stimulation of neuronal activity in glaucoma patients versus controls.
16 glaucoma patients with well controlled IOP (≤22 mmHg, mean 16±3.5 mmHg, mean age 66±14 year) and 20 age matched controls (71±8 years) were included. Vasodilatation upon retinal flicker light stimulation was measured by the dynamic vessel analyser (DVA). Oxygen saturation (SO2, dual - wavelength optical oximetry) was determined and averaged for all arterioles and venules in an annular area centered at the optic disk before and during luminance flicker stimulation (12.5 Hz, modulation depth: 1:20) for 90 s. Furthermore, perimetry was performed in the patients and nerve fiber layer thickness and disk cupping was measured by FD-OCT.
Arterio-venous (A-V) SO2 difference was significantly reduced in the patients vs. controls (26.6±7.5% vs. 30.7±4.2%, p=0.044). Flicker light stimulation impaired the vasodilation in glaucoma patients significantly (p<0.0005) in arterioles (2.0±2.6%) and venules (3.3±2.9%) compared to norm values (6.9±2.8% and 6.5±2.5% respectively). The increase of venous SO2 upon flicker was smaller in the patients than in the controls (1.9±4.9% vs. 4.2±3.7%, p= 0.11). No correlation of any of these parameters with perimetry (mean field defect) or OCT measurements was found.
The reduced vasodilatation upon flicker in glaucoma, found here, is in agreement with Garhofer et al. (J. Glaucoma 13 (2004) 340-4) and may indicate impaired neurovascular coupling (Gugleta et al., Surv. Ophthalmol. 52 (2007) S139-43). This may result in deficits of blood flow regulation explaining the reduced response of venous SO2 to the flicker. The reduced A-V SO2 difference may indicate a lack of oxygen consumption in the retina of glaucoma patients.
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