Mitomycin and the human corneal endothelium
M. L. McDermott, J. Wang and D. H. Shin
Kresge Eye Institute, Wayne State University, Detroit, MI.
OBJECTIVE: To investigate the ultrastructural and physiologic effects of
exposure of the human corneal endothelium to mitomycin at concentrations of
20 micrograms/mL and 200 micrograms/mL using electron microscopy and in
vitro specular perfusion techniques. METHODS: Four pairs of corneas (with
one cornea of each pair receiving balanced salt solution [BSS Plus, Alcon
Laboratories, Fort Worth, Tex] and the other receiving BSS Plus with 20
micrograms/mL of mitomycin) suitable for transplantation, except for
extremes of age or systemic disease, underwent perfusion with corneal
thickness measured serially every 15 minutes followed by fixation for
electron microscopy. Mean corneal swelling rate was calculated for all 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 studies were
performed using two pairs of corneas that received 200 micrograms/mL of
mitomycin. RESULTS: The mean swelling rate for corneas perfused with 20
micrograms/mL of mitomycin (-4.1 microns/h) was not significantly different
from that seen in tissue perfused with BSS Plus (-4.2 microns/h). No
consistent ultrastructural changes could be attributed to exposure to 20
micrograms/mL of mitomycin. Perfusions of mitomycin at 200 micrograms/mL
resulted in prompt corneal swelling with marked ultrastructural alterations
compared with tissue perfused with BSS Plus. CONCLUSION: Human corneal
endothelium may be exposed to undiluted (200 to 500 micrograms/mL)
mitomycin with inadvertent entry into the anterior chamber during
dissection of the scleral flap bed in trabeculectomy followed by
application of mitomycin. This will result in prompt destruction of the
endothelium. Exposure to 20 micrograms/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.
