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 randomly 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 lay on the 120 degree semi-meridian. Corneal topography was performed preoperatively and 1 week and 1 and 3 months postoperatively. Simulated keratometric readings were used to calculate astigmatism amplitude and surgically induced astigmatism (SIA), Postoperative topographic changes were determined by subtracting the preoperative from the postoperative numeric map readings. Results: Three months postoperatively, the mean SIA in the right and left eyes, respectively, was 0.68 diopter (D) +/- 1.14 (SD) and 0.66 +/- 0.52 D in 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 group. Right and left eyes showed similar SIA amplitude but different SiA axis orientation. The SIA was significantly higher in the 5.5 mm CCI group than in the other 2 groups 1 and 3 months postoperatively (P < .01). All groups showed significant wound-related flattening and nonorthogonal steepening at 2 opposite radial sectors. Topographic changes were significantly higher in the 5.5 mm CCI group and significantly lower in the scleral tunnel group. Conclusions: Right and left eyes showed similar SIA amplitude but different SIA axis orientation and topographic modifications, probably because of the different superotemporal and superonasal corneal anatomic structure. The 5.5 mm CCI induced significantly higher postoperative astigmatism, SIA, and topographic changes.