DIFFUSE LUMINANCE FLICKER INCREASES RETINAL VESSEL DIAMETER IN HUMANS

Purpose. To determine retinal vessel diameter variations in response t o neuronal activity induced by diffuse luminance flicker. Methods. The diameter of retinal arteries and veins was measured in 9 normal subje cts by computer analysis of fundus pictures taken in monochromatic lig ht under normal conditions of illumination and after 1 min of sinusoid ally varying diffuse luminance flicker at 10 Hz. Results. The diameter immediately after flicker was significantly larger than the pre-stimu lus diameter by 4.2 +/- 2.2% for the retinal arteries and 2.7 +/- 1.7% for the retinal veins (mean +/- SD). Six s after cessation of the fli cker, arterial diameter was not significantly different from that of p re-flicker value. Conclusions. Diffuse luminance flicker induces an in crease in retinal vessel diameter. This increase most probably reflect s an increase in retinal blood flow previously evidenced in humans by the blue field simulation technique. The technique needs to be optimiz ed in terms of flicker parameters, to determine whether flicker-evoked retinal diameter changes could represent a useful clinical measure of the capability of the retinal vascular system to vasodilate.