Dynamic retinal vessel response to flicker in AMD Retinal vessel responses to flickering light are altered in patients with age-related macular degeneration (AMD) and are not improved after successful Avastin (bevacizumab) therapy.

The retina has the ability to regulate blood flow in response to different metabolic demands. Several animal and human studies demonstrated an increase in retinal vessel diameters as well as in retinal and optic nerve head blood flow during stimulation with diffuse luminance flicker. Like in the brain, blood flow in retinal vessels is strongly coupled to neural activity, which was recently confirmed using laser Doppler flowmetry and retinal vessel diameter measurements.

In 10 patients with exudative AMD [age: median 76 years], retinal vessel reactions were examined by Dynamic Vessel Analyser (DVA) before and 3 months after a single intravitreal application of Avastin. A baseline measurement was followed by three consecutive monochromatic flicker stimulations (530–600 nm, 12.5 Hz, 20 seconds). Temporal retinal vessel reaction was analysed and compared with the reaction in healthy controls.

Mean arterial dilation at the end of flicker was not different in all groups. Maximal dilation occurred in arteries at: pre-treatment, 17.5 seconds; post-treatment, 18.0 seconds; control, 14.5 seconds. In the post-treatment AMD group arterial constriction after stimulation occurred more slowly compared with the control group (p < 0.05).

The investigators conclude that dynamic retinal arterial and venous reactions to flickering light are altered in AMD compared with controls. Three months after a single injection of a vascular endothelial growth factor inhibitor, the investigated retinal dynamic vascular parameters were not altered.

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Acta Ophthalmologica 2010 Jan 22. [Epub ahead of print]