Choroidal microcirculation in Abyssinian cats with hereditary rod-cone degeneration.

Blood flow in the choroid of eyes with retinal degeneration is normally reduced. In the Abyssinian cat, where no changes in choroidal blood flow were observed recently, a closer morphological analysis revealed that two factors might have lead to this finding. (a) The cat's eye consists of a tapetum lucidum where 15.5 microm microspheres cannot reach the precapillary branching in contrast to the non-tapetal areas, where microspheres were located right next to the choriocapillaris. This fact has not yet been described and might be important for further physiological measurements in eyes of species with a tapetum lucidum. (b) The tapetal cells themselves might have a protective role for the choriocapillaris and RPE during retinal degeneration in this specific animal model. Even in late stages of retinal degeneration the RPE and choriocapillaris in areas covered by the tapetum lucidum were not affected whereas non-tapetal areas showed loss of RPE and capillaries.