Surgically induced astigmatism following single site and twin site phacotrabeculectomy augmented with mitomycin C

To determine difference in surgically induced astigmatism (SIA), post-operative intraocular pressure (IOP) and axial length (AL) between single site and twin-site phacotrabeculectomy augmented with Mitomycin C (MMC).

Prospective interventional randomised controlled study.

In a prospective interventional comparative study, eligible patients were scheduled for phacotrabeculectomy. They were randomised to either group A: single site or group B: twin-site phacotrabeculectomy with MMC 0.2 mg/mL. Axial length was measured by using Zeiss IOL master I, pre-operatively and at 1, 3, 6 and 12 months post-operatively. Corneal topography was performed using Bausch and Lomb Orbscan I pre-operatively and at 3, 6 and 12 months post-operatively to analyse surgically induced astigmatism. Vector analysis was used to analyse the surgically induced astigmatism.

One hundred and eight eyes of which 55 patients in group A, and 53 patients in group B were enroled for vector analysis. The mean preoperative astigmatic vector power was +0.89 ± 0.4 D and +0.97 ± 0.5 D in group A and B respectively. The mean post-operative astigmatic vector power was +0.78 ± 0.4 D in group A and +0.96 ± 0.5 D in group B at the end of 12 months. Corneal topography showed post-operative superior flattening (51.8% at 3 months and 55.4% at 12 months) in group A (P = 0.072) compared to superior steepening (59.6% at 3 months and 61.5% at 12 months) in group B (P = 0.977).

The two commonly used techniques of combined cataract and glaucoma surgery proved to be efficacious without significant difference in surgical induced astigmatism.