Neuhann Th, Neuhann I M, Hassel J M
alz augenklinik münchen, Bayerstrasse 3, 80335, München, Deutschland.
Ophthalmologe. 2008 Mar;105(3):241-7. doi: 10.1007/s00347-008-1723-1.
Conventional ablation profiles for excimer lasers for myopic refractive correction of the cornea are of spheric geometry. Therefore, they induce additional imaging aberrations into the optical system of the eye, most notably spherical aberration. This is a major cause of the observed deterioration of visual quality after such corrections, especially under low illumination and ensuing larger pupil diameter. Therefore, aspheric ablation profiles compromizing the preexisting imaging/visual quality of the eye as little as possible are currently being developed and optimized for all laser platforms. Employed methods include customized correction profiles on the basis of individual wavefront data of the anterior corneal topography on the one hand, and correction profiles that minimize the induced spherical aberration in a "standardized" way on the other hand. We demonstrate for a particular laser platform how such profiles must be developed and optimized. Mathematical theoretical calculations appear to be an indispensable but insufficient prerequisite. The biological reaction of the corneal stroma and epithelium ("biodynamic response") can only be determined experimentally and must lead to adjustment of the calculated ablation algorithm. The results show that aspheric profiles developed on this basis can lead to significant reduction of induced spherical aberration. The obtainable effect is, however, limited by the biological response and the ensuing peripheral ablation depth and volume.
用于角膜近视屈光矫正的准分子激光的传统消融轮廓呈球面几何形状。因此，它们会在眼睛的光学系统中引入额外的成像像差，最明显的是球差。这是此类矫正后观察到的视觉质量下降的主要原因，尤其是在低光照和随之而来的较大瞳孔直径情况下。因此，目前正在为所有激光平台开发和优化尽可能少损害眼睛原有成像/视觉质量的非球面消融轮廓。采用的方法一方面包括基于角膜前表面地形的个体波前数据的定制矫正轮廓，另一方面包括以“标准化”方式最小化诱导球差的矫正轮廓。我们展示了对于特定的激光平台，此类轮廓必须如何开发和优化。数学理论计算似乎是必不可少但又不充分的前提条件。角膜基质和上皮的生物反应（“生物动力学反应”）只能通过实验确定，并且必须导致对计算出的消融算法进行调整。结果表明，在此基础上开发的非球面轮廓可导致诱导球差显著降低。然而，可获得的效果受到生物反应以及随之而来的周边消融深度和体积的限制。
