[Study on choroidal blood flow at dark and light adaptation. 1. Choroidal blood flow at dark adaptation]

The effect of dark adaptation on choroidal blood flow (CBF) was studied in albino rabbits. CBF was measured by the hydrogen clearance method. There was no significant change of CBF at dark adaptation in both short term dark adaptation, in which CBF had been expected to increase due to increased oxygen demand of the outer retina, and long term dark adaptation, in which CBF had been expected to decrease due to depressed function of visual cells and retinal pigment epithelium. The results show that dark adaptation does not influence CBF, in spite of the close relationship between the outer retina and the choroidal circulation. The large blood flow of the choroidal circulation may not need the reaction mechanism for the functional changes of the outer retina.