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Martin Hammer, Lisa Ramm, Sven Peters, Lydia Sauer, Regine Augsten; Is Retinal Oxygen Saturation Related to Retinal Nerve Fiber Layer Thickness in Glaucoma Patients?. Invest. Ophthalmol. Vis. Sci. 2014;55(13):2924.
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To investigate whether glaucomatous loss of retinal nerve fibers has impact on oxygen saturation.
45 glaucoma patients (mean age 65.6±12.0 years) were included. Retinal nerve fiber layer (RNFL) thickness was measured circumpapillary by OCT in the superior, temporal, and nasal quadrant (Cirrus OCT, Carl Zeiss Meditec Inc.). Oxygen Saturation (SO2) was measured with the oximetry module of the Retina Vessel Analyzer (Imedos UG) for all arterioles and venules of the same quadrants in a 30 degree field centered at the optic disk. Oximetry readings were averaged for the first quartile of RNFL thickness values and compared to the mean value of the 2nd to 4th quartile (Students T-test).
Nasal SO2-values were significantly higher than superior (arterioles: 99.3±3.9% vs. 97.1±5.5%, p=0.003, venules: 64.2±6.5% vs. 61.2±7.8%, p=0.001) and inferior (arterioles: 99.3±3.9% vs. 97.0±4.4%, p=0.001, venules: 64.2±6.5% vs. 59.4±9.6%, p<0.001) readings. Arterial SO2 was higher in the 1st quartile of RNFL thickness compared to 2nd through 4th quartile for the superior (99.0±6.4% vs. 96.4±5.1%) and nasal (99.7±7.6% vs. 96.1±4.3%) quadrant whereas venous SO2 was lower nasally (62.0±8.5 vs. 64.9±5.7%). The arterio-venous (a-v) SO2 difference was greater for the 1st quartile in all quadrants: (37.5±6.7% vs. 35.4±6.1%, 37.4±8.4% vs. 34.4±5.0%, and 40.4±8.6% vs. 36.7±8.4% respectively). All these differences, however, were non-significant.
SO2 may be altered in patients with severe RNFL loss. Increased a-v differences indicate an insufficient oxygen supply in retinal quadrants with RNFL loss which is consistent with a reduced blood flow found recently (Mitra et al. DOI 10.1016/j.ophtha.2013.10.022).
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