[Induced astigmatism in cataract surgery. Scleral tunneling incisions of 5.5 mm and 6.5 mm after 1-year follow-up].

To evaluate the effect of scleral pocket incisions closed with a single horizontal suture on postoperative astigmatism, 97 patients were enrolled in a prospective study. After 1 year of follow-up the data of 80 patients could be analysed. Routine phacoemulsification was performed in all patients consecutively by one surgeon. 40 patients received a posterior chamber lens with a 5 mm by 6 mm oval polymethylmethacrylate (PMMA) optic (group I), and 40 patients received an intraocular lens with a 6 mm diameter round PMMA optic (group II). The incisions were 5.5 mm and 6.5 mm, respectively. Follow-up visits including keratometry were scheduled 1 day, 5 days, 3 months, 6 months and 1 year postoperatively. The induced astigmatism was calculated using vector analysis. One day after operation the mean induced cylinder was 1.22 D in group I and 1.06 D in group II. After 5 days it amounted to 1.09 D (group I) and 1.03 D (group II), and at 3 months it was 1.07 D and 1.00 D, respectively. Six months after operation the induced cylinder was 1.04 D (group I) and 0.96 D (group II), and at 1 year it was 1.02 D and 0.81 D. There was no statistically significant difference between the groups at any time (Wilcoxon test, P > 0.05). We conclude that scleral pocket incisions closed with a single horizontal suture induce about 1 D of corneal astigmatism, with stability over time. There is no clinical advantage in reducing the incision width by using oval optics.