INTRARETINAL OXYGEN DISTRIBUTION IN RATS AS A FUNCTION OF SYSTEMIC BLOOD-PRESSURE

Differential responses to induced changes in systemic blood pressure ( BP) at different layers of both the retinal and choroidal vasculature were observed, by monitoring localized PO2 as a function of depth, in the retina and choroid of the rat eye using oxygen-sensitive recessed microelectrodes. Visual and electrophysiological localization of the m icroelectrode tip allowed the oxygen distribution to be related to the positions of the vascular beds of the retina and choroid. Highly repr oducible intraretinal PO2 profiles were achieved. The relationship bet ween PO2 and systemic BP was linear in the deep capillary layer of the retina (PO2 = 0.17 x BP - 2.63) and in the choriocapillaris (PO2 = 0. 21 x BP + 2.95), whereas it was nonlinear in the superficial retinal c apillary layer (PO2 = 40.01/[1 + (BP/66.22)(-1.22)]) and deep choroid (PO2 = 83.82/[1 + (BP/124.61)(-0.87)]). The minimum PO2 occurred betwe en the two retinal capillary beds, and a PO2 gradient was evident in t he choroid. The contrasting responses of different layers of the two c irculations reflect different blood flow control mechanisms not eviden t when studying the circulations as a whole.