Comparative Study On Clinical Evaluation And Corneal Topography Of On-flap And Off-flap Epi-LASIK

Purpose:To compare the advantages and disadvantages of on-flap epipolis laser in situ keratomileusis(Epi-LASIK) and off-flap Epi-LASIK.Methods:A prospectively,double-masked and radomized study was performed on 188 eyes of 94 patients.In each patient,one eye underwent on-flap Epi-LASIK (on-flap group) and the fellow eye had off-flap Epi-LASIK(off-flap group).Patients were instructed to rate their pain and other discomfortable symptoms on postoperative day 1,2 and 3;visual acuity,refraction,Haze formation and corneal topography were evaluated 1 month and 4 months postoperatively.Results:1.On postoperative day 1,the difference of subjective mean pain was not statistically significant(P＝0.070);On postoperative day 2 and 3,the difference were statistically significant(P＝0.000 and 0.000).2.On postoperative day 1,2 and 3,the differences between the two groups of photophobia were unstatistical significant(P＝0.455,0.736and 0.085);on postoperative day 1 and 2,the differences between the two groups of tearing were not Statistical significant(P＝0.506 and 0.149),and the differences between eyelid sweep also were not statistical significant(P＝0.366 and 0.740);on postoperative day 3,the differences of tearing and eyelid sweep were statistical significant(P＝0.001 and 0.028)3.The mean epithelial healing time was 2.78±0.51 days in the on-flap group and was 2.34±0.52 days in the on-flap group(n＝94).The difference was not statistically significant(P＝0.018),On the postoperative day 7(n＝74),77.03%of eyes had transparent corneas in the off-flap group and 41.41%in the on-flap group.4.The mean uncorrected visual acuity on postoperative day 7(n＝74) was 1.08±0.38 in the on-flap group and was 1.17±0.35 in the off-flap group,the difference was not statistically significant(P＝0.215);It was 1.24±0.34 in the on-flap group and was 1.42±0.21 in the fellow group at 1 month postoperatively(n＝51),the difference was statistically significant(P＝0.000);It was 1.42±0.21 in the on-flap group and was 1.40±0.21 in the off-flap group at 1 month postoperatively(n＝51),it was not significant differenct(P＝0.485). 5.At 1 month,the mean spherical equivalent was 0.33±0.78 D and 0.24±0.59 D range respectively,at 4 months,they were 0.14±0.46 D and 0.18±0.50 D,all the differences were not statistically significant(P＝0.172 and 0.652).The mean cylinder was 0.20±0.80 D in the on-flap group and 0.11±0.57D in the other group at 1 month after surgery,the difference was statistically significant(P＝0.039),at 4 months, they were 0.27±0.43 D and 0.05±0.46 D with unstatistically significant(P＝0.762).6.On postoperative day 7,the Haze formation was 0.06±0.12 in the on-flap group and 0.03±0.07 in the off-flap group,the difference was statistically significant (P＝0.000),and it peaked the highest at 1 month postoperatively in both groups,but had no significant difference at 1 month and 4 months postoperatively(P＝0.392 and 0.229).7.There were no sighificant differences in the corneal anterior surface radius, corneal anterior elevation,astigmatism and irregularity index between these two groups(P＞0.05).Conclusions:1.The off-flap Epi-LASIK seem to reduce pain ans other uncomfortable symptoms in early postopertative period,the epithelium flap seems to delay the corneal healing time,decrease the cornea transparence and increase the Haze;in late postopertative period,the epithelium flap had no influence on vision,refraction and Haze.2.The uncrrected visual acuity in the two groups improved gradually postoperatively,Haze increased first and then reduced,there almost no haze in the two groups at 4 months postoperatively.3.The on-flap group and off-flap group have the similar infects in changing corneal shapes,astigmatism and irregulatity index postoperatively.The cornea astigmitism and irregulatity were increasing from cornea center to periphery.