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Comparison of standard trabeculectomy versus microtrabeculectomy as a surgical treatment for glaucoma: a randomized clinical trial


Dr Anthony P Wells, Department of Ophthalmology, Wellington Hospital, Riddiford Street, Newtown, Wellington 6021, New Zealand. Email:


Background:  To determine the effect of scleral flap size on the medium-term intraocular pressure control and complication rates after augmented trabeculectomy.

Design:  Prospective randomized clinical trial.

Participants:  Glaucoma patients undergoing primary trabeculectomy. Exclusion criteria included previous ocular surgery apart from cataract surgery, secondary glaucoma and age under 18.

Methods:  Patients were randomized to either standard trabeculectomy (4 × 4 mm scleral flap) or microtrabeculectomy (2 × 2 mm scleral flap), both with adjustable sutures and antimetabolites. Bleb needling was performed as required. Patients were evaluated at day 1, weeks 1, 3, 6 and months 3, 6, 12, 18 and 24 postoperatively.

Main Outcome Measures:  Vision, intraocular pressure, complications and failure (intraocular pressure ≥ 21 mmHg or not reduced by ≥20% from baseline, intraocular pressure ≤ 5 mmHg, repeat glaucoma surgery and no light perception vision).

Results:  Forty-one patients were recruited; 20 had standard trabeculectomy, and 21 had microtrabeculectomy. At 2 years, the mean intraocular pressure and cumulative probability of failure was 12.4 ± 4.6 mmHg and 0.28 for standard trabeculectomy, and 11.5 ± 3.6 mmHg and 0.27 for microtrabeculectomy (P = 0.50 and 0.89, respectively). One patient in each group required Baerveldt device implantation. Vision reduced ≥2 Snellen lines in 15% in the standard trabeculectomy group and 25% in the microtrabeculectomy group, mainly from cataract (P = 0.48).

Conclusion:  Both trabeculectomy techniques achieved good intraocular pressure reduction and had similar complication rates. Scleral flap size had no significant effect on medium-term intraocular pressure control and complication profile.