AIMThe authors investigated the safety and intraocular pressure (IOP) lowering effectiveness of trabeculectomy augmented with mitomycin C application beneath the scleral flap, and assessed the influence of preoperative risk factors on the surgical outcome.
METHODSA retrospective study of 72 consecutive high risk eyes undergoing trabeculectomy with adjunctive mitomycin C (0.2 mg/ml) applied under the scleral flap for 5 minutes was performed. Each eye was ascribed a score based on the number of preoperative risk factors, and categorised into one of three risk factor groups. Success was described as unqualified where IOP was  21 mm Hg without medication and qualified where antiglaucomatous therapy was required to maintain it at such a level. A life table analysis of IOP control was calculated.
RESULTSThe mean IOP (SD) fell from a preoperative level of 28.4 (6.9) to a level of 16.63 (8.06) mm Hg at the last follow up (paired Student's t test: p< 0.0001). Fifty two eyes (72%) were classed as unqualified successes. The survival rates did not differ significantly between different risk factor groups (log rank test: ² = 0.967, p>0.1). The incidence of postoperative complications compared favourably with reports of mitomycin C application between Tenon's capsule and the undissected scleral bed.
CONCLUSIONThe results illustrate that mitomycin C applied beneath the scleral flap during trabeculectomy in high risk eyes is associated with a success rate comparable to other modes of application. The incidence of potentially serious complications such as conjunctival wound leak and prolonged hypotony was lower than previously published data reporting sub-Tenon's administration of mitomycin C. The number and nature of preoperative risk factors do not appear to influence the surgical outcome. A possible mechanism of action is proposed.

Keywords: glaucoma; intraocular pressure; trabeculectomy; mitomycin C