Determining total corneal power after small-incision lenticule extraction in myopic eyes

Abstract

Purpose To evaluate the methods to correct corneal power after myopic small-incision lenticule extraction (SMILE) and to estimate the preoperative corneal power based on postoperative values. Setting Tianjin Eye Hospital, Tianjin, China. Design Retrospective case series. Methods Equivalent keratometry (K) and mean K readings were obtained with the Pentacam HR. The clinical history method was used to calculate the theoretical postoperative K, which was then compared with equivalent K readings. In addition, the anterior–posterior (A–P) method was used to estimate the preoperative mean K. The agreement between computed and actual values was estimated using the Bland-Altman method. Results A significant correlation was observed between the theoretical postoperative K (38.52 diopters [D] ± 1.57 [SD]) and mean K after surgery (39.44 ± 1.43 D) (R2 = 0.9317, P <.001). The mean equivalent K readings at 4.0 mm, 4.5 mm, and 5.0 mm were not significantly different from the theoretical postoperative K values (P =.620, P =.514, and P =.622, respectively). Bland-Altman plots showed a high level of agreement when comparing the theoretical postoperative K with the clinical history K (−0.94 to +0.9 D, −0.83 to +0.88 D, and −0.84 to +0.88 D, respectively). In addition, the estimated preoperative mean K (43.28 ± 1.31 D) derived by the A–P method was comparable to the measured mean K (P =.111). Conclusions Equivalent K readings provided a relatively good estimation of corneal power in eyes after small-incision lenticule extraction. The A–P method might be an option to predict preoperative corneal power. © 2017 ASCRS and ESCRS