Choroidal blood flow. III. Reflexive control in human eyes.

Choroidal blood flow helps maintain a stable temperature environment for the outer retinal layers, especially in the macular area. Recent studies in monkeys have demonstrated a centrally mediated reflexive mechanism that increases choroidal blood flow in response to light or light-generated heat. This increase in choroidal blood flow can be detected as an elevation in ocular surface temperature. With the use of ocular surface temperature as a semiquantitative index of alterations in choroidal blood flow, the existence of a similar reflex was demonstrated in normal human volunteers.