Effects of Conventional Laser Assisted In-Situ Keratomileusis (Lasik) on Spherical Aberrations and Contrast Sensitivity in the Myopic Eyes

Background LASIK is the new surgical procedure for the correction of eyes refractive error. It helps in reducing the patients dependence on glasses & /or contact lenses. But it also increases the spherical aberrations of the eye and reduces contrast sensitivity. Aim To investigate the changes in spherical aberrations, contrast sensitivity & spherical equivalent of the myopic eyes caused by conventional LASIK. Method A prospective, observational study was done in patients with treatable myopic refractive error after undergoing conventional LASIK. Total 29 patients with 56 myopic eyes undergoing LASIK were recruited over a period of six months from Jan 2011 to June 2011 and were followed up for a period of 6 months. Results After LASIK, mean logMAR visual acuity at 1, 3, and 6 was -0.096 which was significantly more as compared to baseline. Pre-operatively mean spherical equivalent was -4.59. There was statistically significant reduction in the mean spherical equivalent post-operatively at 1, 3 & 6 months. Spherical aberration was significantly increased after LASIK (2.71 folds at 1 month, 2.38 fold at 3 months and 2.19 folds at 6 months). Contrast sensitivity (CS) was significantly reduced one month post LASIK for the higher spatial frequencies of 12 and 18 cpd. Conclusion Conventional LASIK significantly increases the postoperative spherical aberrations at 1, 3, and 6 months. It causes significant reduction in CS values at higher frequencies, which recovers to the preoperative levels at 6 months. After LASIK contrast sensitivity at lower spatial frequencies are not significantly altered. LASIK, Spherical aberrations, Contrast sensitivity