J Refract Surg. 2012 Sep;28(9):650-5. doi: 10.3928/1081597X-20120815-08.
To quantify the current accuracy limits of ray tracing for intraocular lens (IOL) calculations, compare results for spherical vs aspheric IOLs, and determine the value of using crystalline lens thickness in IOL calculations.
Of 591 eyes, 363 eyes were implanted with spherical IOLs (320 SA60AT [Alcon Laboratories Inc] and 43 Y-60H [Hoya Corp]) and 228 eyes had aspheric, aberration-correcting IOLs (57 SN60WF [Alcon Laboratories Inc], 112 Tecnis ZCB00 [Abbott Medical Optics], 21 CTAsphina404 [Carl Zeiss Meditec], and 38 iMics1 [Hoya Corp]), all calculated with OKULIX ray tracing (Tedics), based on Lenstar (Haag-Streit) measurements of axial length, corneal radii, and position and thickness of the crystalline lens. The measure of accuracy was the prediction error, ie, the difference between calculated refraction and manifest refraction (spherical equivalent) 1 month after surgery calculated as mean absolute error (MAE).
The prediction error with aspheric IOLs was lower than that with spherical IOLs (MAE 0.27 vs 0.36 D) and was lower for patients with corrected distance visual acuity (CDVA) ⩾1.0 compared to CDVA <1.0 (MAE 0.26 vs 0.38 D). For aspheric IOLs and CDVA ⩾1.0, MAE differed by a factor of two compared to spherical IOLs and CDVA <1.0 (MAE 0.21 vs 0.42 D). Taking the crystalline lens position and thickness into account improved the prediction error by ∼9% overall (MAE 0.33 vs 0.36 D) and was most beneficial in patients with aspheric lenses and CDVA ⩾1.0 (MAE improved from 0.26 to 0.21 D). All differences between the investigated subgroups were statistically significant (P<.05).
Ray tracing for IOL calculation is particularly beneficial with aspheric IOLs and in eyes with good (20/20 or better) postoperative visual acuity.
量化当前光线追踪技术在眼内透镜（IOL）计算中的精度极限，比较球面和非球面 IOL 的结果，并确定在 IOL 计算中使用晶状体厚度的价值。
在 591 只眼中，363 只眼植入了球面 IOL（320SA60AT [Alcon Laboratories Inc] 和 43Y-60H [Hoya Corp]），228 只眼植入了具有像差校正功能的非球面 IOL（57SN60WF [Alcon Laboratories Inc]、112 TecnisZCB00 [Abbott Medical Optics]、21CTAsphina404 [Carl Zeiss Meditec]和 38iMics1 [Hoya Corp]），所有 IOL 均使用基于 Lenstar（Haag-Streit）测量的轴向长度、角膜半径和晶状体位置及厚度的 OKULIX 光线追踪（Tedics）进行计算。准确性的衡量标准是预测误差，即术后 1 个月计算的计算折射与实际折射（等效球镜）之间的差异，以平均绝对误差（MAE）表示。
非球面 IOL 的预测误差低于球面 IOL（MAE 0.27 与 0.36 D），矫正远视力（CDVA）≥1.0 的患者低于 CDVA<1.0 的患者（MAE 0.26 与 0.38 D）。对于非球面 IOL 和 CDVA≥1.0 的患者，与 CDVA<1.0 的患者相比，MAE 的差异为两倍（MAE 0.21 与 0.42 D）。考虑到晶状体位置和厚度，总体上可将预测误差提高约 9%（MAE 0.33 与 0.36 D），对于具有非球面晶状体和 CDVA≥1.0 的患者最有益（MAE 从 0.26 提高到 0.21 D）。所有研究亚组之间的差异均具有统计学意义（P<.05）。
对于具有像差校正功能的非球面 IOL 和术后视力良好（20/20 或更好）的患者，使用光线追踪技术进行 IOL 计算特别有益。
