Corneal topographic changes induced by different oblique cataract incisions

Purpose: To compare astigmatic and topographic changes induced by different oblique cataract incisions. Setting: Department of Ophthalmology, Hospital of San Dong di Piave, Venice , Italy. Methods: One hundred sixty-eight eyes having phacoemulsification were rando mly assigned to 1 of 3 groups: 3.5 mm clear corneal incision (CCI), 60 eyes ; 5.5 mm sutured CCI, 54 eyes; 5.5 mm scleral tunnel, 54 eyes. Incisions la y on the 120 degree semi-meridian. Corneal topography was performed preoper atively and 1 week and 1 and 3 months postoperatively. Simulated keratometr ic readings were used to calculate astigmatism amplitude and surgically ind uced astigmatism (SIA), Postoperative topographic changes were determined b y subtracting the preoperative from the postoperative numeric map readings. Results: Three months postoperatively, the mean SIA in the right and left e yes, respectively, was 0.68 diopter (D) +/- 1.14 (SD) and 0.66 +/- 0.52 D i n the 3.5 mm CCI group, 1.74 D +/- 1.43 D and 1.64 +/- 1.27 D in the 5.5 mm CCI group, and 0.46 +/- 0.56 D and 0.10 +/- 1.08 D in the scleral tunnel g roup. Right and left eyes showed similar SIA amplitude but different SiA ax is orientation. The SIA was significantly higher in the 5.5 mm CCI group th an in the other 2 groups 1 and 3 months postoperatively (P < .01). All grou ps showed significant wound-related flattening and nonorthogonal steepening at 2 opposite radial sectors. Topographic changes were significantly highe r in the 5.5 mm CCI group and significantly lower in the scleral tunnel gro up. Conclusions: Right and left eyes showed similar SIA amplitude but different SIA axis orientation and topographic modifications, probably because of th e different superotemporal and superonasal corneal anatomic structure. The 5.5 mm CCI induced significantly higher postoperative astigmatism, SIA, and topographic changes.