Purpose

To evaluate the accuracy of the measurements of corneal power obtained by ray tracing with a combined Scheimpflug camera–Placido disk corneal topographer (Sirius) in eyes after small incision lenticule extraction for myopia (SMILE).

Methods

Retrospective cases study includes 50 eyes of 50 patients who underwent myopic SMILE. Mean value of simulated keratometry (K_post), mean pupil power (MPP) (ray tracing, diameter of the entrance pupil range 3–6 mm), anterior and posterior corneal radius, and corneal thickness were obtained with Sirius topographer preoperatively and three months postoperatively, as well as cycloplegic refraction. True net power, equivalent keratometry readings, and Haigis equivalent power formula were calculated, and these measurements, MPP and K_post, were compared with the corneal power calculated with the clinical history method (CHM).

Results

Corneal power measurements obtained with all methods were significantly different from CHM (P < 0.001), except the value of MPP obtained at 5.5 mm (P = 0.927). A good direct correlation was found between CHM and all measurements. The distribution of differences as compared with the CHM showed that the lowest difference corresponded to the value of MMP at 5.5 mm (− 0.002 ± 0.6). The Bland–Altman plots for the MPP at 5.5 mm showed 95% limits of agreement between − 1.1787 D and 1.1741 D.

Conclusions

MPP obtained by ray tracing within a diameter of entrance pupil of 5.5 mm could predict corrected corneal power derived from the CHM in eyes following SMILE surgery.

中文翻译：

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联合 Scheimpflug 相机-Placido 圆盘地形图仪通过小切口微透镜提取近视后眼内光线追踪测量角膜屈光力

目的

评估在近视小切口微晶状体提取 (SMILE) 后眼睛中使用联合 Scheimpflug 相机-Placido 圆盘角膜地形图仪 (Sirius) 进行光线追踪获得的角膜屈光力测量的准确性。

方法

回顾性病例研究包括接受近视 SMILE 的 50 名患者的 50 只眼睛。模拟角膜曲率（K _post）、平均瞳孔功率（MPP）（光线追踪，入瞳直径范围 3-6 mm）、前后角膜半径和角膜厚度的平均值是在术前和三个月内用 Sirius 地形图获得的术后，以及散瞳验光。计算真实净功率、等效角膜曲率读数和 Haigis 等效功率公式，并将这些测量值 MPP 和K _post与使用临床病史法 (CHM) 计算的角膜功率进行比较。

结果

 除了在 5.5 mm 处获得的 MPP 值（P  = 0.927）外，所有方法获得的角膜功率测量值均与 CHM 显着不同（P < 0.001）。在 CHM 和所有测量值之间发现了良好的直接相关性。与 CHM 相比的差异分布表明，最低差异对应于 5.5 mm 处的 MMP 值（- 0.002 ± 0.6）。MPP 在 5.5 mm 处的 Bland-Altman 图显示 - 1.1787 D 和 1.1741 D 之间的一致性限制为 95%。

结论

通过在 5.5 mm 入瞳直径内进行光线追踪获得的 MPP 可以预测 SMILE 手术后眼睛从 CHM 获得的校正角膜屈光力。