A randomised, prospective study comparing trabeculectomy augmented with antimetabolites with a viscocanalostomy technique for the management of open angle glaucoma uncontrolled by medical therapy

Abstract

Aims: To compare trabeculectomy with viscocanalostomy for the control of intraocular pressure (IOP) in open angle glaucoma (OAG) uncontrolled by medical therapy.

Methods: 48 patients (50 eyes) with uncontrolled OAG were randomised to either trabeculectomy (25 eyes) or a viscocanalostomy technique (25 eyes). Preoperatively, eyes were graded in terms of risk factors for drainage failure. Those undergoing trabeculectomy were given intraoperative antimetabolites (5-fluorouracil 25 mg/ml (5-FU), mitomycin C (MMC) 0.2 mg/ml and 0.4 mg/ml) according to a standard protocol. Antimetabolites were not used intraoperatively in eyes undergoing viscocanalostomy, but they were randomised to the use of viscoelastic (Healonid GV) for intraoperative intracanalicular injection.

Results: There were no significant differences between the groups in age, sex, type of OAG, preoperative medications, risk factors for drainage failure, and preoperative IOP. Mean follow up was 19 months (range 6-24 months). It was 12 months or longer in all eyes, except one lost to follow up at 6 months. At 12 months, complete success (IOP <21 mm Hg without antiglaucoma medications) was seen in all eyes undergoing trabeculectomy (100%), but in only 64% of eyes undergoing viscocanalostomy (p<0.001). The mean IOP was lower at 12 months (p<0.001) with trabeculectomy and the number of eyes with IOPs of 15 mm Hg or less was greater (p<0.05). The mean IOP at 12 months was lower in eyes that had undergone viscocanalostomy using intraoperative intracanalicular Healonid GV injection compared to those where only balanced saline solution had been used (p<0.01). However, in terms of complete success there was no difference between the viscocanalostomy groups (p<0.1). With the exception of measurements at 1 week, visual recovery (logMAR acuity) was similar and laser flare and cell values showed little differences between the groups. Corneal topography and keratometry at 12 months were little different from preoperative values. Postoperative interventions (subconjunctival 5-FU and needling procedures) were similar between the groups. Transient complications such as early bleb leak and hyphaema were more common in the trabeculectomy group (p<0.05). Postoperative cataract formation was more common after trabeculectomy (p<0.05).

Conclusions: IOP control appears to be better with trabeculectomy. Viscocanalostomy is associated with fewer postoperative complications, although significant complications permanently impairing vision did not occur with either technique.

Figure 1

(A) and (B) Photographs of two eyes 18 months after viscocanalostomy with successful drainage, showing evidence of a small drainage blebs.

Figure 2

Mean intraocular pressure with time. Comparison of trabeculectomy (n=25) with viscocanalostomy (n=23). *Denotes time points where significant differences between the groups were found.

Figure 3

Mean intraocular pressure with time. Comparison of trabeculectomy (n=25) with viscocanalostomy where only balanced saline solution (BSS) had been used for intracanalicular injection (n=11) and viscocanalostomy where viscoelastic (Healonid GV) had been used (n=12). *Denotes times where significant differences between the three groups were found.

Figure 4

Unaided and pinhole logMAR visual acuity with time.

Figure 5

Mean laser flare values with time for trabeculectomy (n=25) and viscocanalostomy (n=23).

Figure 6

Mean laser cell values with time for trabeculectomy (n=25) and viscocanalostomy (n=23). *Denotes times where significant differences between the groups were found.