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

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.

Tianjin Eye Hospital, Tianjin, China.

Retrospective case series.

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.

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).

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.