Influence of LASIK on higher order aberrations of myopic eyes

Objective:To observe and analyze the influence of LASIK on higher order aberrations in myopic eyes. To discuss the correlation between higher order aberrations and corneal refractive power (K1,K2),and the correlation between higher order aberrations and corneal thickness.Methods:Sixty four myopic eyes (33 cases) were evaluated by the Allegretto Wave Analyzer at pre LASIK,and 1 month and 10 months after LASIK. The root mean square (RMS) values of higher order aberrations were calculated for each eye when the pupil was dilated. Corneal refractive power and corneal thickness were measured by an Orbascan Ⅱ and corneal topography was assessed at the time of each examination.Results:Before LASIK,the constituent ratio of lower order aberrations was 81.7%,and coma and other higher order aberrations accounted for 13.9% and 4.4%,respectively. One month after surgery,higher order aberrations had increased significantly (P0.05). The constituent ratios of lower order aberrations and coma and other higher order aberrations were 27.8%,51.8%,and 20.9%,respectively. Ten months after LASIK,higher order aberrations had decreased with the constituent ratios of lower order aberrations,coma and other higher order aberrations. Their respective values were 38.1%,40.8%,and 17.0%. Coma and spherical aberrations returned to preoperative levels. There was a significant positive correlation between severity of myopia and the total number of higher order aberrations after surgery (P0.05). There was no significant correlation between the total number of higher order aberrations and corneal refractive power or corneal thickness preoperatively (P0.05),but the correlation became significant after surgery (P0.01).Conclusion:Conventional LASIK increases higher order aberrations. Higher order aberrations after surgery may tend to decrease with time. The higher the myopia was,the number of higher order aberrations were much greater after surgery.