A LONG-TERM DOSE-RESPONSE STUDY OF MITOMYCIN IN GLAUCOMA FILTRATION SURGERY

Objective: To establish the long-term, dose-response relationship betw een the concentration of and duration of exposure to mitomycin to a de crease in intraocular pressure (IOP) and fewer complications. Methods: We performed a prospective double-masked, placebo-controlled, I-year study evaluating the decrease in IOP and fewer complications of fornix -based trabeculectomy surgery in 300 eyes equally divided among therap y with placebo; mitomycin, 0.2 mg/ mL, applied for 2 minutes; mitomyci n, 0.2 mg/mL, applied for 4 minutes; or mitomycin, 0.4 mg/mL, applied for 2 minutes. All of the eyes had vertical and horizontal cup-disc ra tios greater than 0.7. Results: We observed significant treatment-rela ted differences in IOP, with a decrease in IOP in all 3 mitomycin-trea ted groups for all of the times beyond 1 month. The number of eyes ach ieving strict IOP control and the development of cataract suggest a po ssible dose-response effect for concentration and time of exposure. Pr ogressive lens opacification was the most frequent complication in 54 eyes (18.1%). The incidence of progressive lens changes markedly incre ased in subjects receiving 4 minutes of mitomycin therapy. Cataract fo rmation was unrelated to IOP. Other complications were rare. Macular f olds developed in 6 patients, with visual acuity returning to better t han 20/40 in all but 1 patient. Conclusions: A possible dose-response relationship seemed to exist between the concentration of and duration of exposure to mitomycin. Length of exposure seems to be more importa nt than concentration. The benefits of additional decreases in IOP mus t be weighed against the potential for increases in the risk of compli cations.