A long-term dose-response study of mitomycin in glaucoma filtration surgery
A. L. Robin, R. Ramakrishnan, R. Krishnadas, S. D. Smith, J. D. Katz, S. Selvaraj, G. L. Skuta and R. Bhatnagar
Department of International Health, School of Hygiene and Public Health, Johns Hopkins University, Baltimore, Md, USA.
OBJECTIVE: To establish the long-term, dose-response relationship between
the concentration of and duration of exposure to mitomycin to a decrease in
intraocular pressure (IOP) and fewer complications. METHODS: We performed a
prospective double-masked, placebo-controlled, 1-year study evaluating the
decrease in IOP and fewer complications of fornix-based trabeculectomy
surgery in 300 eyes equally divided among therapy with placebo; mitomycin,
0.2 mg/ mL, applied for 2 minutes; mitomycin, 0.4 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 ratios greater than 0.7. RESULTS: We
observed significant treatment-related differences in IOP, with a decrease
in IOP in all 3 mitomycin-treated groups for all of the times beyond 1
month. The number of eyes achieving strict IOP control and the development
of cataract suggest a possible dose-response effect for concentration and
time of exposure. Progressive lens opacification was the most frequent
complication in 54 eyes (18.1%). The incidence of progressive lens changes
markedly increased in subjects receiving 4 minutes of mitomycin therapy.
Cataract formation was unrelated to IOP. Other complications were rare.
Macular folds developed in 6 patients, with visual acuity returning to
better than 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
important than concentration. The benefits of additional decreases in IOP
must be weighed against the potential for increases in the risk of
complications.
