COMMENTARY

Comparing Different Concentrations of MMC for Primary Trabeculectomy

Shuchi B. Patel, MD

Disclosures

August 27, 2015

Evaluating the Long-term Efficacy of Short-Duration 0.1 mg/mL and 0.2 mg/mL MMC in Primary Trabeculectomy for Primary Adult Glaucoma

Sihota R, Angmo D, Chandra A, Gupta V, Sharma A, Pandey RM
Graefes Arch Clin Exp Ophthalmol. 2015;253:1153-1159

Study Summary

The adjunctive use of an antifibrotic agent has significantly increased the success of trabeculectomy surgery. The most commonly used antifibrotic agent is mitomycin C (MMC).

The rates of surgical success vary depending on the concentration of and time of exposure to MMC. The dose of MMC, as described in the literature, has varied in concentration (0.1-0.5 mg/mL) and duration (0.5-5 min). A higher dose of MMC has been reported to lead to lower intraocular pressures (IOPs) and a higher trabeculectomy success rate, but also more frequent complications.

Few randomized studies have compared doses or durations of application of MMC. In particular, there are even fewer studies on low doses of MMC.

This prospective randomized study compared two low concentrations of MMC—0.1 mg/mL and 0.2 mg/mL—applied subconjunctivally for 1 minute in patients with no previous history of ocular surgery. All patients who were enrolled required surgery for uncontrolled primary open-angle glaucoma or chronic angle-closure glaucoma despite maximal medical therapy.

Patients were randomly assigned to receive either 0.1 mg/mL or 0.2 mg/mL for 1 minute intraoperatively after creation of the scleral flap but before the sclerostomy. The concentrations of and duration of exposure to MMC were significantly less than what most physicians are using in their practice. Complete success (IOP ≤ 15 mm Hg) at 2 years was seen in 92% of patients who received 0.1 mg/mL and in 91.7% of those who received 0.2 mg/mL.

The complications (eg, leaking blebs, overfiltration, and hypotony) that occur more commonly with higher doses of MMC were much lower at these concentrations. However, bleb morphology suggested that with the 0.2-mg/mL dose of MMC, the blebs appeared to have larger areas of thinning and were therefore at a higher risk of leaking in the future. In contrast, the lower concentration did not have a higher failure rate due to scarring, suggesting that lower doses are similarly efficacious in preventing fibrosis.

This study suggests that intraoperative use of a lower dose of MMC, even with a short duration, may be better to achieve a successful trabeculectomy without an increased risk for complications. Administration of higher doses, whether through higher concentrations or longer exposure time, may be unnecessary.

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