Retinal arterial occlusion leads to acidosis in the cat

This study investigated the changes in pH during retinal artery occlusion by means of extracellular H⁺ concentration ([H⁺] _o) measurements in the retina under both air and 100% O₂ ventilation. Occlusion was produced in intact anesthetised cats by pressing with a probe onto a retinal artery. [H⁺]_o profiles were recorded across the retina with pH sensitive microelectrodes. The average inner retinal [H⁺]_o increased during occlusion, resulting in an acidification of as much as 0·10 pH units, even under 100% O₂ ventilation. The inner retinal H⁺ profile magnitude decreased during occlusion due to impaired clearance. The average outer retinal H⁺ profile magnitude also increased even though outer retinal H⁺ production did not increase during occlusion. This might be due to H⁺ diffusion from the inner retina to the outer retina, which is opposite to the flux in the normal retina. After reperfusion, [H⁺]_o returned to its preocclusion value. In conclusion, arterial occlusion leads to acidification of the retina. Enhanced oxygenation during occlusion did not decrease this acidification. This may explain why increasing PO₂ in the retina by enhanced O₂ breathing improves retinal function during and after occlusion, but does not totally reverse the effect of occlusion.