Hydrogen peroxide and corneal endothelium.

Because of recent evidence of low levels of hydrogen peroxide in the aqueous humor, studies were performed to determine levels of corneal endothelial toxicity as well as factors modifying toxicity. Perfusion of cornea endothelial cells for 3 h with varying concentrations of hydrogen peroxide demonstrated a threshold of toxicity at a concentration between 0.3 and 0.5 mM H2O2. The toxic effect resulted in rapid corneal swelling as well as disruption of endothelial cell cytoplasm and organelles. Both the physiologic and anatomic toxic effects of 0.5 mM H2O2 could be blocked with 5400 U/ml catalase. Exposure of corneas to 20 mM H2O2 for 10 min in the presence of EDTA - Fe+3 resulted in an enhancement of corneal swelling rate more rapid than that which resulted from a 10 min exposure to 20 mM H2O2 alone. Neither the presence of ascorbic acid nor the absence of glutathione and adenosine had and effect on the cornea swelling rate which occurred during a 3 h perfusion of endothelium with 0.3 mM H2O2. Chelated iron had no effect on the corneal swelling induced by phototactivation of rose bengal presensitized cornea endothelial cells.