Perez et al. investigated the effects of subconjunctival mitomycin C (MMC) on the rates of hypertensive phase (HP) after the implantation of Ahmed Glaucoma Valves (AGV). Their retrospective, comparative, single-surgeon study indicates that intra and postoperative injections of MMC may reduce the occurrence of HP in these eyes. Their protocol included one injection (0.1 ml of 0.25 mg/ml MMC) over the plate intraoperatively, followed by injections one and four weeks postoperatively. A total of 20 eyes underwent AGV implantation without MMC and 17 eyes underwent AGV implantation with MMC. All eyes had a minimum follow-up of 6 months. HP, defined as IOP > 21 mmHg during the first three postoperative months, occurred in 17.6% (3/17) of the MMC-treated eyes and 55% (11/20) of the control group (p = 0.04). There was no significant difference in mean IOPs at six months (14.0±0.8 mmHg and 14.7±0.9 mmHg for the MMC and control groups, respectively; p=0.6)), but the MMC group required significantly less medications (1.2±0.2 vs. 2.2±0.3 in the control group; p = 0.007). Few complications were reported, including one case of punctate keratitis and one eye with lid swelling.
Although previous RCTs have not been able to demonstrate a benefit of intraoperative MMC in eyes undergoing AGV implantation, some retrospective case series have suggested that 5FU/MMC injections may promote better IOP control postoperatively. As suggested by the authors, limitations of this study include its retrospective nature, the small sample size and the short-term follow-up. The design of a double-masked, prospective, randomized trial would avoid selection bias, illustrated in this series, for example, by a different proportion of NVG eyes in the MMC group (60%) and the control group (35%).
In a previous study,1 we hypothesized that the unsuccessful use of MMC may be explained by the presence of a foreign body, a constant stimulus for fibroblastic proliferation, which may overcome the antiproliferative properties of MMC. A minimum follow-up of one year would be required in order to confirm that this will not happen with this treatment protocol. Furthermore, the authors did not compare success rates of both groups using predefined criteria and Kaplan-Meyer survival curves. In conclusion, as mentioned by the authors, RCTs with a greater number of eyes and longer follow up are needed to evaluate if MMC injections improve the success rates of AGV implantation.
RCTs with a greater number of eyes and longer follow up are needed to evaluate if MMC injections improve the success rates of AGV implantation