MITOMYCIN AND THE HUMAN CORNEAL ENDOTHELIUM

Objective: To investigate the ultrastructural and physiologic effects of exposure of the human corneal endothelium to mitomycin at concentra tions of 20 mu g/mL and 200 mu g/mL using electron microscopy and in v itro specular perfusion techniques. Methods: Four pairs of corneas (wi th one cornea of each pair receiving balanced salt solution [BSS Plus, Alcon Laboratories, Fort Worth, Tex] and the other receiving BSS Plus with 20 mu g/mL of mitomycin) suitable for transplantation, except fo r extremes of age or systemic disease, underwent perfusion with cornea l thickness measured serially every 15 minutes followed by fixation fo r electron microscopy. Mean corneal swelling rate was calculated for a ll four experiments, and the control group that received BSS Plus was compared with the group that received mitomycin using a paired t test. Electron micrographs were examined in a masked fashion. Similar studi es were performed using two pairs of corneas that received 200 mu g/mL of mitomycin. Results: The mean swelling rate for corneas perfused wi th 20 mu g/mL of mitomycin (-4.1 mu m/h) was not significantly differe nt from that seen in tissue perfused with BSS Plus (-4.2 mu m/h). No c onsistent ultrastructural changes could be attributed to exposure to 2 0 mu g/mL of mitomycin. Perfusions of mitomycin at 200 mu g/ml resulte d in prompt corneal swelling with marked ultrastructural alterations c ompared with tisssue perfused with BSS Plus. Conclusion: Human corneal endothelium may be exposed to undiluted (200 to 500 mu g/mL) mitomyci n with inadvertent entry into the anterior chamber during dissection o f the scleral nap bed in trabeculectomy followed by application of mit omycin. This will result in prompt destruction of the endothelium. Exp osure to 20 mu g/mL of mitomycin, a level exceeding the concentration that may be present in the aqueous humor after its proper application, appears nontoxic in this system.