Human Ocular Vasodynamic Changes in Light and Darkness

Purpose: To determine whether changes in the retinal blood flow in light and darkness occur in humans. METHODS; The systolic and diastolic flow velocities were measured by color Doppler in the ophthalmic and the central retinal arteries in 12 healthy individuals in light and darkness.

Results: In the ophthalmic artery there was a trend toward lower systolic velocity in darkness compared with that in the light, but there was no change in diastolic velocity. In the central retinal artery the systolic and the diastolic flow velocities were markedly increased in darkness. After re-exposure to light the systolic flow velocity decreased.

Conclusions: Darkness is associated with increased blood flow velocity in the central retinal artery, probably reflecting increased retinal metabolic demands by the photoreceptors.