The Study Of Corneal Wavefront Aberration Of Laser Epithelial Keratomileusis And Epipolis Laser In Situ Keratomileusis

Purpose To investigate the characteristics of corneal wavefront aberrations of Laser epithelial keratomileusis and Epipolis laser in situ keratomileusis versus Laser in situ keratomileusis.Method The 32 low to moderate myopic eyes of 32 patients with spherical equivalent(SE) lower than -6.00D were randomized into two groups.LASEK was performed in the study group and LASIK with the microkeratome of 110um head in the control group.Meanwhile the 36 high myopic eyes of 36 patients with spherical equivalent(SE) from -6.00D to -10.00D were randomized into another two groups. The study group underwent Epi-LASIK and the control group underwent LASIK with the microkeratome of 90um head.There were no significant differences in preoperative age,sex,manifest refraction,corneal higher-order aberrations and ocular higher-order aberrations between the study and control groups.Uncorrected visual acuity(UCVA),subjective manifest refraction,best corrected visual acuity(BCVA), ocular wavefront aberration,the corneal shape and the contrast sensitivity and glare sensitivity were examined preoperatively and 6 months postoperatively. Hartmann-Shack aberrometer(WASCA,Carl Zeiss Meditec) was used to measure the ocular aberration in scotopic pupil and the aberrations were analyzed at the pupil size of 5 mm.Corneal anterior and posterior surface heights were acquired by Oculus Pentacam.And then anterior and posterior corneal wavefront aberrations were reconstructed by Matlab software at the 5mm pupil size for analysis.The variance analysis and t test in a mixed model were used by SPSS 12.0 for statistical analysis.P value of＜0.05 was considered statistically significant.Results Six months postoperatively,in 5mm analytic diameter,in both study and control groups,the anterior and posterior corneal 3^th order aberrations and spherical aberrations increased(P＜0.05).The changes of corneal spherical aberration in LASEK group and Epi-LASIK group were(0.186±0.042) um and(0.290±0.129) um, both fewer than LASIK-110 and LASIK-90 respectively(P＜0.05).In LASEK group, the increasements of anterior corneal spherical aberration and posterior corneal spherical aberration were(0.813±0.451) um and(-0.627±0.273) um.And in Epi-LASIK group those were(0.897±0.504) um and(-0.607±0.341) um.The increasement of anterior corneal spherical aberration in study group was less than that in control group(P＜0.05),while the increasement of posterior corneal spherical aberration in study group was similar to that in control group(P＞0.05).In 5mm analytic diameter,fewer changes in RMS of 3^th,4^th,5^th order aberrations and coma, spherical aberration were noted in study group than in control group.There were no statistical significant differences between the study group and control group(P＞0.05) except for the increasement of spherical aberration between Epi-LASIK and LASIK-90 groups(P＜0.001).Six months postoperatively,in LASEK group,56% of the eyes had a UCVA over 1.2 and 44%over 1.0,and in Epi-LASIK group,6%of the eyes had a UCVA over 1.0,66%over 0.8 and 28%over 0.6,with no significant differences to the study group.In LASEK group 81%of the eyes maintained the same BCVA and 19%had 1 line better BCVA.In Epi-LASIK group 72%and 22%eyes had the same and 1 line better BCVA,while 6%eyes dropped 1 line.There were no significant differences of UCVA and BCVA between the study groups and control groups(P＞0.05).Conclusions The corneal 3^th order aberration and the corneal spherical aberration increase after LASEK/Epi-LASIK.Fewer corneal spherical aberration,anterior corneal spherical aberration and ocular wavefront aberrations are induced in LASEK/Epi-LASIK than in LASIK.LASEK/Epi-LASIK provide safe and reliable ways of correcting myopia with less surgically induced wavefront aberrations.