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Sylvana Ventzke, Dirk Sandner, Eberhard Spoerl, Lutz Pillunat, Richard Stodtmeister; Dynamic Vessel Analysis May Show an Improvement of Endothelial Function by Intravitreal Ranibizumab in Diabetic Macular Edema. Invest. Ophthalmol. Vis. Sci. 2013;54(15):2415.
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Retinal arterial vasoconstriction has been observed after application of ranibizumab in age-related macular degeneration. Changes in retinal vessels may be expected following treatment with ranibizumab in patients with diabetic macular edema. We investigated the response of the diameter of retinal arterioles and venoles to flicker stimulation by classifying the registrations of the flicker reaction in these patients in addition to the quantitative evaluation.
Patients: N=30. Age: 60±11 years. Male/female:16/14. Inclusion criterion: Clinically significant macular edema. Dynamic Vessel Analysis (Imedos, Jena, Germany) consisting of a Fundus Camera, video equipment and computer-aided process control: Online measurement of the diameter of a retinal arteriolar and a venolar vessel segment, 50s baseline, three times 20s flicker stimulation and 80s follow up registration. Three registrations were averaged. Examination time points: Before the first injection (Examination 1: E1), before second (E2) and third injection (E3) and 3 month after the first injection (E4). Vessel reactions were classified in four classes: Class(C)1: Within normal limits. C2: Reduced, clearly visible. C3: very reduced, but recognizable in spite of noise. C4: Absent. The observer was masked by encoding the examination time point and the patients.
The reaction of the arterioles didn’t change significantly from E1 through E4 . The reaction of the venoles showed a trend to a monotonous improvement (Friedman-Test: p=0.089). Arith. mean of classes±std.deviation: E1: 2.17±1.17. E2: 2.07±0.98. E2: 1.97±1.06. E3:1.97. E4: 1.63±0.85. Friedman-test: p=0.09. Wilcoxon-test: E1vsE4: 0.054 after Bonferroni-Holm adjustment.
Experienced observers are often better in detecting and judging biological signals buried in noise than machines. Therefore we applied the technique of classification in our noisy registrations. An increase in diameter of arterioles and venoles might be a sign of autoregulation which is clearly seen in healthy subjects and may be reduced in diabetes mellitus. A shift to one of our lower classes may be interpreted as an improvement in autoregulation which is initiated by the vascular endothelium. Our results may be the sign of an improvement of retinal vessel endothelial function by ranibizumab.
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