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S.-F. G. Seidova, K. E. Kotliar, C. P. Lohmann, I. M. Lanzl; Dynamic Retinal Vessel Response to Flicker in AMD Patients Before and After a Single Intravitreal Bevacizumab Injection. Invest. Ophthalmol. Vis. Sci. 2007;48(13):3353.
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Exposure of the retina to flickering light induces retinal vessel dilation in healthy subjects. The effect is termed neurovascular coupling. Vessel responses are assumed to be different in various diseases and can be improved after successful therapy. Bevacizumab inhibits VEGF which is also needed for regular vascular function. We investigated arterial and venous vessel response to flicker light application in AMD patients before and after treatment with a single intravitreal bevacizumab injection.
In 10 patients with exudative AMD (age: (median(1 quantile; 3 quantile): 76,0(73.5;80.0) years), retinal arterial and venous vessel reactions were examined by Dynamic Vessel Analyzer (DVA) before and 3 months after a single intravitreal application of bevacizumab (1.25 mg). A baseline measurement was performed for 50 s followed by 3 consecutive monochromatic rectangular luminance flicker stimulations (wave lengths: 530-600 nm, frequency: 12.5 Hz, duration: 20 s) with a 80 s observation pause between flicker stimulations. We performed non-parametrical statistical data analysis of the measured parameters independent from the commercial DVA program. Data was compared to age matched healthy controls.
Average venous reaction in the AMD group before treatment differed significantly from the control (p<0.05). Pretreatment arterial reaction was not significantly different in both groups. There was no difference in average arterial or venous vessel reaction in the pretreatment compared to the posttreatment measurement (p>0.05). The mean of maximal flicker dilation for arteries amounted to: pretreatment: 2.0(1.2;4.6)%; posttreatment: 2.4(1.7;4.1)%; control: 2.1(1.6;3.8)%. For veins this parameter amounted to: pretreatment: 3.4(2.3;5.0)%; posttreatment: 4.1(3.4;4.8)%; controls: 5.0(3.7;5.8)%. In individual cases the venous reaction was improved after injection with faster and larger increase in diameter during stimulation. In AMD pre- and posttreatment arterial dilation during stimulation occurred slower in comparison to the control group.
Retinal veins in AMD show impaired reaction to flicker stimulation in comparison to normal age matched arterial reaction. One single intravitreal bevacizumab injection does not change retinal vessel reaction to flicker in the examined group 3 months after the application. Further investigations with more patients and longer observation times are needed in order to understand the possible role of arterial and venous regulation in AMD and its treatment.
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