Performing "safe surgery" remains as the sine qua non for using antimetabolites safely and effectively as an adjunct to trabeculectomy. However, there are some strategies that can be incorporated in the surgical technique to reduce the risk of complications resulting from the application of anti-scarring medication, said Richard K. Parrish, II, MD, at the World Ophthalmology Congress.

"One cannot do a technically unsatisfactory filtration procedure and expect an anti-scarring medication to rescue a fundamental surgical error," said Dr. Parrish of the Bascom Palmer Eye Institute at the University of Miami in the United States. "Minimizing preoperative subconjunctival inflammation, surgical trauma, and immediate postoperative hypotony are concepts that were critical before we had anti-scarring agents and still are today."

However, experience with anti-scarring agents has taught several lessons. The first is the importance of never placing the filtration site inferiorly. In addition, in order to create a more diffuse posterior bleb, the flap should be fornix-based, not limbus-based, and the intraoperative mitomycin-C should be applied over a larger area (3 or 4 clock hours) versus a more limited region.

Other safety considerations include use of intraoperative 5-fluorouracil 50 mg/mL for 5 minutes as an alternative to mitomycin-C in older Caucasians undergoing primary surgery. If the choice is made to use mitomycin-C in such patients, then a lower concentration — 0.2 or 0.4 mg/ml versus 0.5 mg/mL — and for a shorter exposure time — 2 minutes versus 5 minutes — might also be considered to reduce the likelihood of creating a very thin, avascular conjunctiva.

Dr. Parrish also noted that in his personal technique, he uses a cellulose sponge to absorb any excessive mitomycin-C prior to irrigation in the hopes of preventing distribution of the agent over the surgical field.

"I have no evidence this is beneficial, but it seems to make good sense," he said.