Risk of bleb-related infection appears low after trabeculectomy with MMC

The authors report interim results of the first prospective study to examine the incidence, severity and prognosis of bleb infection following trabeculectomy with mitomycin C with or without phacoemulsification and IOL implantation. They found that the risk of bleb-related infection in this cohort at 2.5 years was low, at 1.5 percent, compared with rates reported in previous retrospective studies. However, the probability of bleb infection was significantly increased in cases with bleb leakage compared with those without it (5.8 ± 4.1 vs. 1.2 ±0.5 percent).

This study presents interim data from the Collaborative Bleb-related Infection Incidence and Treatment Study for 908 glaucoma patients (908 eyes) who underwent surgery at one of 34 clinical centers in Japan. Nine eyes developed a bleb-related infection. Kaplan-Meier survival analysis revealed that the probability of developing a bleb-related infection was 1.5 ± 0.6 percent (cumulative probability ± standard error) at the 2.5-year follow-up among the trabeculectomy cases and 1.4 ± 1.0 percent among the combined surgery cases. The rate was 1.5 percent both in cases with a limbal-based flap and in those with a fornix-based flap.

The authors say that these prospective findings reveal a relatively low incidence of bleb-related infection in cases treated with adjunctive mitomycin C compared with retrospective studies. One explanation for the favorable result may be the study's prospective fashion and protocol. The study's participants were warned about bleb-related infection in detail and thus were more cautious than ordinary patients. And they were all followed by glaucoma specialists. The data do not support claims of a higher probability of postoperative bleb-related infection in limbus-based conjunctival flaps, although the authors say that such a pattern could still emerge with prolonged follow-up. The finding that the development of bleb infection was significantly different between cases with bleb leakage and those without it is consistent with a previous report of increased bleb infection in cases with conjunctival leakage.

This is a commendable effort on an important subject. The small number of cases that developed infection likely make it harder to study specific risk factors for infection, as well as to comment on the profile of infectious agents causing blebitis in Japan. However, it would have been useful if the article included descriptions of some of the clinical features of patients who developed bleb infection, such as bleb morphology, the concentration of mitomycin C and the duration of exposure used in these infected blebs.