角膜的非球面形态及角膜屈光手术对其的影响

Corneal asphericity and the effects of the corneal refractive surgery on it

角膜的非球面形态是指正常人眼角膜多为非球面的扁椭圆形，这种形态有助于提高视觉质量。不同的人眼角膜非球面系数Q值并不相同，多数为负值，各文献报道的角膜Q值正常值差异较大，角膜Q值受多种因素影响，不同象限对Q值影响较大，年龄对其影响较小，近视度数、眼轴长度、曲率半径、球差等与Q值均有一定的相关性。角膜屈光手术是矫正屈光不正的重要途径之一，但其对角膜非球面性的影响可导致眩光、视觉质量下降等问题，不同手术方式对其影响不同。波前像差引导的准分子激光原位角膜磨镶术（LASIK）、Q值引导的LASIK对Q值的影响均较标准LASIK小，而飞秒激光角膜基质透镜取出术（FLEx）对Q值的影响又较波前像差引导的LASIK小，近年开展较多的飞秒激光制瓣准分子激光原位角膜磨镶术（FS-LASIK）、微小切口基质透镜取出术（SMILE）对角膜非球面性的影响则鲜有报道。另外，近视角膜屈光手术后Q值向正值变化，而远视手术后则向负值变化，Q值的变化量与等效球镜度呈高度正相关，激光、愈合反应等对角膜非球面性的影响尚需进一步探索。对角膜非球面性及角膜屈光手术的研究有助于获得更好的术后视觉质量，就角膜的非球面形态及不同角膜屈光手术方式对其的影响进行综述。

The corneal aspherieity refers to most normal corneal surface is an aspherical flat oval,which is helpful to improve the visual quality. In most cases, corneal aspherieal coefficient Q-value is negative, and different normal Q-value is reported in literatures, corneal Q-value is influenced by many factors, quadrants have great effects on it, the influence of age is weak, there are correlation between myopic degree, ocular axial length, radius of curvature,intraoeular pressure and Q-value. The corneal refractive surgery is one of the most important methods to correct refractive errors,but it has negative effects on the corneal asphericity, and then results in glare, visual quality degradation and other issues. Different corneal refractive surgeries would have different effects on the corneal asphericity. Wavefront aberration-guided femtoseeond laser in situ keratomileusis（LASIK） surgery and Q-value guide LASIK are superior to standardized LASIK, the change of Q-value after femtoseeond lenticule extraction （FLEx） surgery is less than that after wavefront aberration guided LASIK. The influence of femtosecond laser in situ keratomileusis （FS-LASIK） and small incision lenticule extraction （SMILE） on Q-value are rarely reported. In addition, the Q-value changes from negative to positive after corneal refractive surgery of myopia, the variation tendency is opposite after hyperopia surgery. Q-value variation is highly correlated to spherical equivalent,the impact of laser and healing still needs further exploration. In order to further exploring of the corneal asphericity and getting a better effect of surgery, here is a review about normal corneal aspherieity and the effects of the corneal refractive surgery on it.