Surgically induced astigmatism following glaucoma surgery in Egyptian patients.

PURPOSE: The altered visual function induced by changes in corneal curvature following filtration surgery is distressing to patients. The aim of this study was to evaluate surgically induced astigmatism following trabeculectomy in comparison with deep sclerectomy.

METHODS

In a prospective interventional comparative study, patients with primary open-angle glaucoma were randomly allocated to either group A or B; deep sclerectomy with mitomycin C 0.2 mg/mL and trabeculectomy with mitomycin C 0.2 mg/mL, respectively. Keratometry was performed using Topcon KR-7000P autokerato-refractometer preoperatively and at 6 months postoperatively. Vector analysis was used to analyze the surgically induced astigmatism.

RESULTS

Sixty eyes of 45 patients in group A, and 60 eyes of 42 patients in group B were enrolled for vector analysis. The mean preoperative astigmatic vector power was -0.49±1.65 D and +0.47±2.18 D in groups A and B, respectively. The mean postoperative astigmatic vector power was -1.14±1.55 D in group A and -0.35±1.8 D in group B. The mean change in astigmatic vector powers was -0.67±1.63 D in group A and -0.82±2.0 D in group B. When compared with preoperative data in either group, the differences were significant, P=0.001 & 0.007 in groups A and B respectively, whereas the postoperative difference between either group was insignificant (P=0.723). A total of 40% of corneas got flatter in group B compared with 25% in group A, P=0.057.

CONCLUSIONS

Both trabeculectomy and deep sclerectomy induced considerable postoperative astigmatism. A longer follow-up period is recommended to study the different patterns of astigmatism in either procedure.