Kwon Young, Choi Myoung, Bott Steven
Alcon Labs, 2501 Discovery Dr. Orlando, FL 32826, USA.
Opt Express. 2008 Aug 4;16(16):11808-21. doi: 10.1364/oe.16.011808.
We developed a rigorous simulation model to evaluate ablation algorithms and surgery outcomes in laser refractive surgery. The model (CASIM: Corneal Ablation SIMulator) simulates an entire surgical process, which includes calculating an ablation profile from measured wavefront errors, generating a shot pattern for a flying spot laser beam, simulation of the shot-by-shot ablation process based on a measured or modeled beam profile, and healing of the cornea after surgery. Using simulated post-surgery corneal shapes for various ablation parameters and beam fluences, we calculated angular dependence of ablation efficiency and the amount of increase in corneal asphericity. Without considering the effect of corneal healing, our result shows the following; 1) ablation efficiency reduction in the periphery depends on the peak fluence of the laser beam, 2) corneal asphericity increases even in the surgery using an ablation profile based on the exact Munnerlyn formula, contrary to previous reports, and 3) post-surgery corneal asphericity increases by a smaller amount in high fluence small Gaussian beam surgery than in low fluence truncated Gaussian beam. Our model can provide improved ablation profiles that compensate for the change of corneal asphericity and induction of spherical aberration in a flying spot laser system, resulting in better surgery outcomes in laser refractive surgeries.
我们开发了一个严格的模拟模型，用于评估激光屈光手术中的消融算法和手术结果。该模型（CASIM：角膜消融模拟器）模拟整个手术过程，包括根据测量的波前误差计算消融轮廓、生成飞点激光束的光斑图案、基于测量或建模的光束轮廓模拟逐点消融过程以及手术后角膜的愈合情况。利用针对各种消融参数和光束能量密度模拟的术后角膜形状，我们计算了消融效率的角度依赖性以及角膜非球面性增加的量。在不考虑角膜愈合影响的情况下，我们的结果如下：1）周边消融效率的降低取决于激光束的峰值能量密度；2）与先前的报告相反，即使在使用基于精确芒纳林公式的消融轮廓进行手术时，角膜非球面性也会增加；3）在高能量密度小高斯光束手术中，术后角膜非球面性的增加量比低能量密度截断高斯光束手术中的增加量小。我们的模型可以提供改进的消融轮廓，以补偿飞点激光系统中角膜非球面性的变化和球差的诱导，从而在激光屈光手术中实现更好的手术效果。
