The choroidal circulation has presented a challenging problem to investigators who have attempted to determine its basic physiology. Few attempts have been made to study this rich vascular coat of the eye, and the approach to the problem has varied. The opaque sclera in higher animals has been a constant obstacle to the external approach to these vessels. Only recently have reports appeared of observations made by means of the external approach to determine the response of the choroidal vessels to various chemical and nervous stimuli.*
Emphasis has been focused on this vascular coat of the eye in recent years by the anatomic contributions of Ashton4 and Wybar.† Many ocular diseases may be attributed directly or indirectly to choroidal vascular disease. The role of the choroid in the problems of glaucoma, sympathetic ophthalmia, the Sturge-Weber syndrome, choroideremia, and retinal detachments, along with a variety of other pathologic ocular processes,