Effect on astigmatism of the location of clear corneal incision in phacoemulsification of cataract

PURPOSE: To investigate the refractive results of clear corneal incision performed at the steepest meridian of pre-existing corneal astigmatism. METHODS: One hundred eighty-two patients with astigmatism > 0.75 diopters (D) were evaluated. Superior, temporal, nasal, superotemporal, or superonasal clear corneal incisions were performed at the steep meridian. Refraction, visual acuity, and topography values were evaluated, and changes in surgically induced astigmatism were calculated by vector analysis using the Fourier formula. Paired t test was used to compare mean values. RESULTS: Postoperative cylinder values showed minor changes in all groups, except the nasal group. Nasal incision increased preoperative cylinder from 1.13 D to 1.83 D 6 months after surgery. Temporal and superotemporal incisions resulted only in small astigmatic changes. Conversely, superior, superonasal, and nasal incisions induced more pronounced astigmatism. CONCLUSIONS: Performing clear corneal incision for phacoemulsification of cataract at the steep meridian resulted in small changes with temporal incisions, whereas nasal incisions resulted in higher surgically induced astigmatism.