Surgical treatment of glaucoma is usually reserved for serious cases which cannot be controlled by other means such as topical medication or laser. Surgery can be performed in most types of glaucoma in order to reduce the pressure inside the eye which if left uncontrolled can irreversibly damage the optic nerve leading to loss of sight. There are a number of variants of drainage surgery but the most commonly performed procedure is trabeculectomy in which a guarded channel is fashioned through the wall of the eye under the upper lid and the fluid is allowed to collect under the conjunctiva (the membrane lining the eyeball) to form a drainage bleb. Scarring during the healing process can cause this channel to close and the operation to fail with a rise in pressure. Mitomycin C is a powerful agent which prevents scarring by inhibiting the multiplication of cells which produce scar tissue. This review asks whether there is evidence that its use during the initial stages of surgery to prevent the excessive conjunctival scarring reduces the risk of failure of the operation. Three types of patient were included: those at high risk of failure because of previous failed surgery or other complications, those having combined cataract and glaucoma surgery and those having primary trabeculectomy - an operation for the first time for their glaucoma. The review found evidence that Mitomycin C reduces the risk of surgical failure in both high risk and primary surgery but no evidence on combined cataract and glaucoma surgery. But the risk of adverse effects including an increased risk of cataracts (not in the combined group) was also noted. There were only a few studies on each category of patients and most were of only poor or moderate quality.
Intraoperative MMC reduces the risk of surgical failure in eyes that have undergone no previous surgery and in eyes at high risk of failure. Compared to placebo it reduces mean IOP at 12 months in all groups of participants in this review. Apart from an increase in cataract formation following MMC, there was insufficient power to detect any increase in other serious side effects such as endophthalmitis.
Trabeculectomy is performed as a treatment for glaucoma to lower the intraocular pressure (IOP). Mitomycin C (MMC) is an antimetabolite used during the initial stages of a trabeculectomy to prevent excessive postoperative scarring and thus reduce the risk of failure.
To assess the effects of intraoperative MMC compared to placebo in trabeculectomy.
We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (which contains the Cochrane Eyes and Vision Group Trials Register) (The Cochrane Library Issue 4, 2009), MEDLINE (January 1966 to January 2010), EMBASE (January 1980 to January 2010), LILACS (Latin American and Caribbean Health Sciences Literature Database) (January 1982 to January 2010), OpenSIGLE (January 2010) and the UK Clinical Trials Gateway (UKCTG) (January 2010). We also wrote to investigators of trials included in the review to ask if they were aware of any other studies. There were no language or date restrictions in the search for trials. The electronic databases were last searched on 19 January 2010.
We included randomised controlled trials (RCTs) of intraoperative MMC compared to placebo or no adjunct in trabeculectomy surgery.
Two authors independently assessed trial quality and extracted data. We contacted trial investigators for missing information.
Eleven trials, involving a total of 698 participants, were included. The trials enrolled three types of participants (high risk of failure, trabeculectomy combined with cataract surgery, no previous surgical intervention). Mitomycin C appears to reduce the relative risk of failure of trabeculectomy both in eyes at high risk of failure (relative risk 0.32, 95% confidence interval: 0.20 to 0.53) and those undergoing surgery for the first time (relative risk 0.29, 95% confidence interval 0.16 to 0.53). No significant effect on failure was noted in the group undergoing trabeculectomy combined with cataract extraction. Mean IOP was significantly reduced at 12 months in all three participant groups receiving MMC compared to placebo. No significant increase in permanent sight-threatening complications was detected. However, none of the trials were large enough or of sufficient duration to address the long-term risk of bleb infection and endophthalmitis which has been reported in observational studies. Some evidence exists that MMC increases the risk of cataract.