School of Optometry and Ophthalmology, Eye Hospital, Wenzhou Medical University, Wenzhou, China.
Key Laboratory of Vision Science, Ministry of Health PR China, Wenzhou, China.
Ophthalmic Res. 2021;64(1):85-90. doi: 10.1159/000507963. Epub 2020 Apr 20.
To evaluate the effect of constant C for ray tracing-assisted intraocular lens (IOL) power calculation in patients with different refractive power, we compared the refractive outcome of the ray tracing method based on constant C and conventional IOL calculation.
215 eyes which underwent phacoemulsification and IOL implantation were enrolled in the study. According to the average corneal power, patients were divided into 3 groups: high corneal power (K >45 D) group, medium corneal power (43 ≤ K ≤ 45 D) group, and low corneal power (K <43 D) group. The predicted sphero-equivalent refractive outcome for the IOL power implanted at surgery was calculated using the ray tracing method, SRK/T, and Haigis formulas.
On the basis of the corneal refractive power, there were 65 eyes of K >45 D (30.23%), 96 eyes of 43 ≤ K ≤ 45 D (44.65%), and 54 eyes of K <43 D (25.12%). In general, the ray tracing group had the smallest value of mean absolute error (MAE) and mean error, and the proportions of eyes with absolute error (AE) <0.50 and <0.75 D were significantly higher than those of the other 2 formulas (p = 0.010). In each group, the value of MAE was smallest in the ray tracing group; for the proportions of AEs <0.50 and <0.75 D, the values in the ray tracing group were higher than those in the SRK/T and Haigis groups. Especially in the high and low corneal refractive groups, the proportion of AE <0.25 D was also obviously higher, but only in the low corneal refractive power group, and the difference was statistically significant (p = 0.006).
Compared with the conventional formulas, C constant of the ray tracing-assisted IOL power calculation has more accuracy for the patients with different corneal refractive powers. Ray tracing could provide better guidance for IOL selection clinically.
评估恒量 C 在不同屈光力患者中的光线追踪辅助人工晶状体（IOL）屈光力计算的效果，我们比较了基于恒量 C 的光线追踪方法和常规 IOL 计算的屈光结果。
共纳入 215 例接受白内障超声乳化吸除术和 IOL 植入术的患者。根据平均角膜屈光力，患者分为 3 组：高角膜屈光力（K>45 D）组、中角膜屈光力（43≤K≤45 D）组和低角膜屈光力（K<43 D）组。使用光线追踪法、SRK/T 和 Haigis 公式计算术后植入 IOL 的预测等效球镜屈光结果。
基于角膜屈光力，有 65 只眼 K>45 D（30.23%）、96 只眼 43≤K≤45 D（44.65%）和 54 只眼 K<43 D（25.12%）。一般来说，光线追踪组的平均绝对误差（MAE）和平均误差最小，AE<0.50 和<0.75 D 的眼比例明显高于其他 2 个公式（p=0.010）。在每组中，光线追踪组的 MAE 值最小；对于 AE<0.50 和<0.75 D 的比例，光线追踪组的值高于 SRK/T 和 Haigis 组。特别是在高和低角膜屈光组中，AE<0.25 D 的比例也明显更高，但仅在低角膜屈光力组中，差异具有统计学意义（p=0.006）。
与常规公式相比，光线追踪辅助 IOL 屈光力计算的恒量 C 对不同角膜屈光力的患者更准确。光线追踪可以为临床 IOL 选择提供更好的指导。
