Temperature modulating action of choroidal blood flow.

A major physiologic role for the high flow choroidal vasculature is to help maintain a stable temperature in the macula. The choroidal vasculature modulates tissue temperature in the macula via both active and passive mechanisms. The active mechanisms involve a reflexive increase in choroidal blood flow in response to light. The neuro-anatomical pathways mediating this reflective mechanism have been demonstrated to involve the supra-chiasmatic and the Edinger-Westphal nuclei. The importance of the thermal environment for the retina has been neglected in looking for causes of retinal disease. The observations on the ability of the choroidal circulation to modulate the thermal environment of the macula should excite further study of the role of temperature and the ability of the eye to dissipate light-generated heat on macula disease.