Moreno-Barriuso E, Lloves J M, Marcos S, Navarro R, Llorente L, Barbero S
Instituto de Optica Daza de Valdés, Consejo Superior de Investigaciones Científicas, Serrano 121, 28006 Madrid, Spain.
Invest Ophthalmol Vis Sci. 2001 May;42(6):1396-403.
To determine objectively the changes in the ocular aberrations (3rd order and above) induced by myopic LASIK refractive surgery and its impact on image quality.
The ocular aberrations of 22 normal myopic eyes (preoperative refraction ranged from -13 to -2 D) were measured before (2.9 +/- 4.3 weeks) and after (7.7 +/- 3.2 weeks) LASIK refractive surgery using a laser ray tracing technique. A set of laser pencils is sequentially delivered onto the eye through different pupil locations. For each ray, the corresponding retinal image is collected on a CCD camera. The displacement of the image centroid with respect to a reference provides direct information of the ocular aberrations. Root-mean-square (RMS) wavefront error was taken as image quality metric.
RMS wavefront error increased significantly in all eyes but two after surgery. On average, LASIK induced a significant (P = 0.0003) 1.9-fold increase in the RMS error for a 6.5-mm pupil. The main contribution was due to the increase (fourfold, P < 0.0001) of spherical aberration. The increase in the RMS for a 3-mm pupil (1.7-fold) was also significant (P = 0.02). The modulation transfer (computed for 6.5-mm pupil) decreased on average by a factor of 2 for middle-high spatial frequencies.
(1) Laser ray tracing is a well-suited, robust, and reliable technique for the evaluation of the change of ocular aberrations with refractive surgery. (2) Refractive surgery induces important amounts of 3rd and higher order aberrations. The largest increase occurs for spherical aberration. Decentration of the ablation pattern seems to generate 3rd order aberrations. (3) This result is important for the design of customized ablation algorithms, which should cancel existing preoperative aberrations while avoiding the generation of new aberrations.
客观确定近视性准分子激光原位角膜磨镶术（LASIK）屈光手术引起的眼像差（三阶及以上）变化及其对图像质量的影响。
使用激光光线追踪技术，测量22只正常近视眼睛（术前屈光度范围为-13至-2D）在LASIK屈光手术前（2.9±4.3周）和术后（7.7±3.2周）的眼像差。一组激光束通过不同的瞳孔位置依次投射到眼睛上。对于每条光线，相应的视网膜图像在电荷耦合器件（CCD）相机上采集。图像质心相对于参考点的位移提供了眼像差的直接信息。均方根（RMS）波前误差用作图像质量指标。
除两只眼睛外，所有眼睛术后RMS波前误差均显著增加。平均而言，对于6.5mm的瞳孔，LASIK导致RMS误差显著（P = 0.0003）增加1.9倍。主要原因是球差增加（四倍，P < 0.0001）。对于3mm的瞳孔，RMS增加（1.7倍）也很显著（P = 0.02）。对于中高空间频率，调制传递（针对6.5mm瞳孔计算）平均降低了2倍。
（1）激光光线追踪是一种非常适合、稳健且可靠的技术，用于评估屈光手术引起的眼像差变化。（2）屈光手术会引起大量的三阶及更高阶像差。球差增加最大。消融模式的偏心似乎会产生三阶像差。（3）这一结果对于定制消融算法的设计很重要，该算法应消除现有的术前像差，同时避免产生新的像差。
