Trabeculectomy: evaluation of the area exposed to mitomycin C

PurposeMitomycin C (MMC) is used to increase the durability of filtering procedures in glaucoma. However, the ideal time and area of exposure, as well as the associated side effects remain to be fully understood. This study aims to analyse the association of the MMC‐exposed area in trabeculectomy with safety and efficacy outcomes.MethodsProspective, interventional pilot study of 25 eyes of 25 open‐angle glaucoma patients enrolled for a primary trabeculectomy with MMC 0.4 mg/ml. The antimetabolite solution was visually highlighted by mixing it with a vital dye (trypan blue 0.1%). The area of MMC application was evaluated using a software analysis program (ImageJ). The primary outcome was the association of surgical intraocular pressure (IOP) lowering efficiency with the area of MMC application. Absolute success was defined as 30% IOP reduction and less than 18 mmHg, with no further medication. Relative success was similarly defined but IOP‐lowering medication was used.ResultsThe mean MMC‐exposed area was 122.6 ± 40.0 mm² (median 116 mm²). The mean time of follow‐up was 7.2 ± 4.8 months. Mean IOP reduction after trabeculectomy was 12.5 ± 8.0 mmHg with absolute and relative success rates of 60% and 76%, respectively. Overall, no relationship between the MMC‐exposed area and parameters of efficacy nor safety were observed (p = 0.40). Interestingly, all patients with a MMC exposure area >150 mm² had a 100% absolute success rate. All failed trabeculectomies (6 eyes, 24% of the total) had a MMC‐exposed area <150 mm². Lastly, only (but one) patients with MMC‐exposed area <150 mm² needed more than on laser suture lysis.ConclusionsOur study gives an approximate absolute value of the MMC‐exposed area during trabeculectomy and suggests it may be related to the hypotensive efficacy, with exposed MMC areas >150 mm² being associated with better IOP‐lowering outcomes.