The width of the light reflex on retinal arteries and veins

A computerized microdensitometric technique was applied to fundus photographs of 40 young male subjects. The width of the blood column and the width of the central light reflex were measured on 240 arteries and 240 veins of various sizes. No light streaks were registered on vessels of caliber less than 50 micron. The ratio of the widths: light streak/blood column showed wider reflexes on small (less than 100 micron) compared to larger (greater than or equal to 100 micron) vessels in both arteries and veins (P less than 0.01). Small retinal veins had wider light streaks than small arteries (P less than 0.01). The results of these objective measurements are partly in conflict with previous ophthalmoscopic observations, and we challenge accepted views on clinical interpretation on reflectivity differences in normal retinal vessels. Our results are discussed on a background of hemodynamics of microcirculatory flow.