Effects of steep-axis incision on corneal curvature in onehanded phacoemulsification

AIM: To examine the effects of one-handed phacoemulsification with steep-axis incision on corneal curvature and analyze surgically induced astigmatism（SIA） on the true net power, anterior and posterior corneal surfaces. METHODS: Patients with cataracts underwent onehanded phacoemulsification with a 2.4-mm steep-axis of clear corneal incision（CCI） based on true net power. CCI was created under the guidance of Verion. Central corneal thickness（CCT）, keratometry readings of the true net power and anterior and posterior corneal surface were obtained using Pentacam. Biometry, such as axial length, anterior chamber depth（ACD） and white-to-white（WTW） were performed using Lenstar pre-and 3 mo postoperatively. RESULTS: The study evaluated 68 eyes of 65 patients. The mean age was 65.93±9.40 y; CCT was 529.21±37.40 μm; WTW was 11.59±0.35 mm. Regarding true net power, keratometric value at the flattest corneal meridian for the 3-mm central zone（Ks） was significantly decreased postoperatively（P=0.031）. Keratometric value at the steepest corneal meridian for the 3-mm central zone（Kf） was increased postoperatively（P＞0.05）. Astigmatism of true net power was 1.21±0.56 D preoperatively and significantly decreased to 1.02±0.58 D postoperatively（P=0.021）. On the anterior corneal surface, no significant difference in Ks and Kf was noted pre-versus postoperatively. Anterior corneal astigmatism was 1.08±0.51 D preoperativelyand significantly decreased to 0.87±0.46 D postoperatively（P=0.002）. On the posterior corneal surface, Ks and Kf were significantly increased postoperatively（all P＜0.05）, and posterior corneal astigmatism also increased（P=0.008）. The SIA values of true net power and the anterior and posterior corneal surfaces at 3 mo postoperatively were 1.26±0.63 D（range: 0.11 to 2.80 D）, 1.05±0.54 D（range: 0.23 to 2.40 D）, and 0.21±0.17 D（range: 0.01 to 0.07 D）, respectively. CONCLUSION: One-handed phacoemulsification with steep-axis incision can effectively decrease astigmatism of true net power and anterior corneal astigmatism. In the same surgery, the difference in personal SIA potentially originated from a difference in personal corneal thickness and diameter, both CCT and WTW distance should always be measured preoperatively when planning steep-axis phacoemulsification.