gms | German Medical Science

The exposition of the retina to flickering light is followed by retinal vessel dilation. A standardization of the properties of flickering light so far has not been undertaken in different laboratories. The vessel response to green-blue and green-red flickering light with different exposure frequency was examined in our study.

In 10 young, healthy volunteers the Retinal Vessel Analyzer (RVA) was applied to asses retinal arterial diameters. A baseline measurement was performed for one minute. Then a flicker light alternating between the colors red (600 - 720 nm) - green (530 - 570 nm) and blue (430 - 520 nm) - green (530 - 570 nm) with a flicker frequency of 2, 6, 12, 16 or 20 Hz was applied for 30 sec. All experiments were repeated 3 times. The experiment using 12 Hz stimulation was repeated after 1 week with the same volunteers.

With both tested chromatic flickering lights a prompt vessel dilation of retinal arteries in comparison to baseline could be determined in all volunteers (p<0.001). On average with red-green flicker this amounted to 2.0%±1.1% after 2 Hz stimulation; to 2.9%±1.1% at 6 Hz; to 3.5%±1.4% at 12 Hz; to 3.1%±1.2% at 16 Hz and to 1.8%±0.9% at 20 Hz. With blue-green flicker we found a dilation of 1.7%±1.1% after 2Hz stimulation, of 2.5%±1.1% at 6 Hz; of 3.4%±1.1% at 12 Hz; of 2.7%±1.2% at 16 Hz and of 1.8%±0.8% at 20 Hz. The repeat experiment using 30 sec stimulation after one week showed no statistical difference to the first series (p>0.2).

Flickering light of 30 sec leads to a prompt and reproducible vessel dilation of retinal arteries. An increase in magnitude of dilation could be noted with increased stimulus frequency from 2 Hz to 12 Hz. The maximal amplitude of dilation decreases if the stimulus frequency increases further from 12 Hz to 20 Hz. We therefore think, that flicker application of 12 Hz flicker stimulus constitutes a feasible basis for examinations of retinal vessel behavior, with good dilation magnitude and low patient inconvenience.