Department of Ophthalmology, the Keck School of Medicine of the University of Southern California, Los Angeles, California, USA.
J Cataract Refract Surg. 2013 May;39(5):739-44. doi: 10.1016/j.jcrs.2012.11.031.
To establish a corneal correction equation for the Shammas post-hyperopic laser in situ keratomileusis (LASIK) (Shammas-PHL) formula and to evaluate its accuracy in cases with and without available pre-LASIK data.
Private practices, Lynwood, California, and Mesa, Arizona, USA.
Retrospective comparative observational study.
The corrected corneal power (Kc) was calculated in each eye by adding the refractive change at the corneal level to the pre-LASIK keratometric (K) readings. By comparing Kc with the measured post-LASIK K readings (Kpost), the following equation was derived: Kc = 1.0457 Kpost-1.9538. This equation was combined with the Shammas original formula to obtain the Shammas-PHL formula.
The new formula was evaluated in 18 eyes with previous LASIK data and in 24 eyes with no previous LASIK data. Using the Shammas-PHL formula, the mean arithmetic prediction error was -0.03 diopter (D) ± 0.72 (SD) (range -1.57 to +1.54 D) and the median absolute error was 0.38 D in 18 eyes with available pre-LASIK data and 0.05 ± 0.58 D (range -0.56 to +1.40 D) and 0.43 D, respectively, in the 24 eyes with no pre-LASIK data.
The Shammas-PHL formula can be used in post-hyperopic LASIK cases whether or not the pre-LASIK data are available.
建立 Shammas 远视后准分子激光原位角膜磨镶术（LASIK）（Shammas-PHL）公式的角膜矫正方程，并评估其在有和无可用 LASIK 术前数据的情况下的准确性。
美国加利福尼亚州林伍德和亚利桑那州梅萨的私人诊所。
回顾性比较观察研究。
在每只眼中，通过将角膜水平的屈光变化添加到 LASIK 术前角膜（K）读数中，计算校正后的角膜力量（Kc）。通过将 Kc 与测量的 LASIK 术后 K 读数（Kpost）进行比较，得出以下方程：Kc = 1.0457 Kpost-1.9538。将该方程与 Shammas 原始公式相结合，得到 Shammas-PHL 公式。
在 18 只具有先前 LASIK 数据的眼中和 24 只没有先前 LASIK 数据的眼中评估了新公式。使用 Shammas-PHL 公式，在有可用 LASIK 术前数据的 18 只眼中，平均算术预测误差为-0.03 屈光度（D）±0.72（SD）（范围-1.57 至+1.54 D），中位数绝对误差为 0.38 D；在 24 只没有 LASIK 术前数据的眼中，分别为 0.05 ± 0.58 D（范围-0.56 至+1.40 D）和 0.43 D。
Shammas-PHL 公式可用于远视后 LASIK 病例，无论是否有 LASIK 术前数据。
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