A Comparison of Hepes and Bicarbonate Buffered Intraocular Irrigating Solutions: Effects on Endothelial Function in Human and Rabbit Corneas

These studies were undertaken to evaluate the effects of a HEPES-buffered intraocular irrigating solution on endothelial ultrastructure and function in perfused human and rabbit corneas. Rabbit corneas perfused with the HEPES solution swelled at a rate of 26.5 ± 2.2 μm/hr, while control corneas perfused with GBR did not swell over 3 hr of perfusion. In the HEPES-perfused human corneas, temperature reversal was inhibited and the corneas swelled slightly. BSS Plus-perfused human controls deswelled at — 16.6 ± 3.5 μm/hr. Scanning and transmission electron microscopy revealed no significant differences in ultrastructure between HEPES-perfused and control corneas. Na+K+ATPase activities of endothelial homogenates were reduced nearly 25% in HEPES buffer compared to bicarbonate. The results of this study indicate that HEPES-buffered Ringer's solution cannot maintain proper function of the corneal endothelium because of its lack of bicarbonate ion and because of the toxicity of HEPES on endothelial Na+K+ATPase.