Mitomycin Not Associated With Complication in Trabeculectomy

Jenni Laidman

March 12, 2015

Contrary to previous studies, the antimetabolite mitomycin was not associated with an increase in complication rates, according to a study published online March 5 in JAMA Ophthalmology.

Jessica A. Olayanju, BS, a medical student at Mayo Clinic College of Medicine, Rochester, Minnesota, and colleagues conducted a retrospective, population-based review of 334 patients and 460 eyes undergoing trabeculectomy for glaucoma between January 1, 1985, and December 31, 2010, at the Mayo Clinic and Olmsted Community Hospital, Olmsted County, Minnesota. The investigators reviewed patient records to determine the occurrence of complications including bleb leak, hypotony, hyphema, choroidal effusion, choroidal hemorrhage, blebitis, and endophthalmitis in relation to mitomycin concentrations administered during surgery.

Researchers found that the 20-year cumulative chance of any complication was 45.0% (95% confidence interval [CI], 38.0% - 52.0%), but the rate of trabeculectomy-related complications did not appear to be associated with mitomycin use during a mean follow-up of 7.7 years. The association rate of complications and mitomycin dose was P = .77.

Shan Lin, MD, a clinical spokesperson for the American Academy of Ophthalmology and director of Glaucoma Service at the University of California, San Francisco, Department of Ophthalmology, told Medscape Medical News that the mitomycin finding may represent increased experience with the antimetabolite. "It is possible that greater knowledge of the risks of mitomycin use has led to surgeons adapting their techniques to avoid these complications. This may include more detailed closure of the conjunctival wound to avoid leakage and low eye pressure." Dr Lin was not involved in the study.

However, the lower complication rate could be an artefact of study design, he noted. "A major limitation of this study is that is retrospective and subject to reporting bias. Minor complications such as bleb leak or choroidal effusions can be under-reported because the doctor does not specifically check for this or observes a minor aspect and does not record it because it is likely to resolve spontaneously."

Of the 460 eyes undergoing trabeculectomy, 159 had complications. In 100 eyes, complications occurred within the first 3 months after surgery. In 59 eyes, complications occurred later than 3 months. Ten eyes experienced both early and late complications.

The 20-year cumulative chance of early complication was 19.7% (95% CI, 16.2% - 23.6%), and for late complication, it was 26.0% (95% CI, 15.0% - 36.0%). The risk for vision-threatening complications over the course of 20 years for blebitis was 2.0% (95% CI, 0% - 4.0%), and 5.0% (95% CI, 1.0% - 9.0%) for endophthalmitis. Complications led to further surgical procedures in 98 (21.3%) cases.

Complication rates in this study are "on par with prior studies of trabeculectomy," Dr Lin told Medscape Medical News, pointing out that the rate includes minor complications that can be fixed or will resolve over time.

The authors note that Mayo Clinic reduced the concentration of mitomycin used in trabeculectomy in 2007 from 0.4 to 0.2 mg/mL in an attempt to lower the number of complications, although surgeons could increase the concentration in patients with other risk factors for failure.

However, the study found no significant difference in complication rates, whatever the mitomycin concentration. Among 221 eyes that received no mitomycin, 74 (33.5%) developed any complication and four (1.8%) developed endophthalmitis. In comparison, among 88 eyes treated with a 0.2 mg/mL dose of mitomycin, 22 (25.0%) developed any complication and 2 (2.3%) developed endophthalmitis; among the 151 eyes treated with a 0.4 mg/mL dose, 35 (23.2%) developed any complication and 2 (1.3) developed endophthalmitis.

The research found that age, sex, ethnicity/race, family history, prior cataract extraction, or prior laser trabeculoplasty were not predictors of late trabeculectomy complications (P > .10). Men had a higher rate of severe complications than women, at 39 (29.3%) of 133 vs 27 (13.4%) of 201.

Among the entire study population, regardless of mitomycin treatment, the most frequent early complications were hyphema, microhyphema, hypotony, bleb leak, and choroidal effusion or hemorrhage.

The most frequent late complication was bleb leak, followed by hypotony and late choroidal effusion.

This study was supported in part the National Institutes of Health, Research to Prevent Blindness Inc, and the Mayo Foundation for Medical Education and Research. The authors and Dr Lin have disclosed no relevant financial relationships.

JAMA Ophthalmol. Published online March 5, 2015. Abstract

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