Effects of steep meridian incision on corneal astigmatism in phacoemulsification cataract surgery

PURPOSE: To evaluate surgically induced astigmatism (SIA) when the clear corneal incision is located on the preoperative steep meridian of the corneal astigmatism in phacoemulsification cataract surgery. SETTING: Seoul St. Mary's Hospital, Seoul, South Korea. DESIGN: Comparative case series. METHODS: Patients with preoperative corneal astigmatism greater than 0.50 diopter (D) were evaluated. The corneal incision meridian was chosen by rounding the steep corneal meridian to the closest 10 degrees. All incisions were enlarged to 3.0 mm before intraocular lens implantation. Patients were grouped according to incision location (temporal, superotemporal, superior). Preoperative keratometric data were compared with data collected 2 months postoperatively. Polar value analysis was used to analyze the SIA. The Hotelling trace test was used for comparison of intraindividual changes. RESULTS: The study evaluated 95 patients (30 eyes temporal incision, 32 eyes superotemporal incision, 33 eyes superior incision). Two months postoperatively, the combined mean polar values for SIA changed significantly in the temporal group (Hotelling T(2) = 0.418; P=.008), superotemporal group (Hotelling T(2) = 1.078; P<.001), and superior incision group (Hotelling T(2) = 1.175; P<.001). The SIA was 0.28 @ 79, 0.40 @ 85, and 0.46 @ 92, respectively. CONCLUSIONS: Choosing the corneal incision based on the preoperative steep meridian significantly decreased keratometric astigmatism at the temporal, superotemporal, and superior locations. Thus, it is desirable to place the corneal incision on the steep meridian in eyes with corneal astigmatism higher than 0.50 D.