Comparison of inflammatory cytokines in tears when off-flap and on-flap Epi-LASIK are used

Abstract

Objective To compare the release rate of inflammatory cytokines in tears and the clinical outcomes for off-flap epi-LASIK eyes and the contralateral on-flap Epi-LASIK eyes; to explore the possible mechanisms for the clinical differences.Methods This prospective and randomized study enrolled 18 myopic patients who underwent off-flap Epi-LASIK in one eye (off-flap group) and on-flap Epi-LASIK in the contralateral eye (on-flap group).Tears were collected from each eye preoperatively and 2 hours,1 day and 5 days postoperatively.Concentrations of intedeukin-lβ (IL-1β),IL-6,IL-8 and tumor necrosis factor α (TNFα) were measured by a multiplex immunobead assay.The release rate (tear fluid flow-corrected concentration) was calculated by multiplying the concentration by tear fluid flow.Uncorrected visual acuity (UCVA),refraction,best-corrected visual acuity,haze score,and percentage of corneal epithelial healing were also evaluated.Data were analyzed using a paired t test,Wilcoxon rank sum test,and a chi-square test.Results Compared with the on-flap group,the off-flap group had better UCVA outcomes (t=-4.832,P＜0.01) and higher percentages of epithelial healing (Z=5.861,P＜0.01) at 5 days after surgery,and lower levels of haze at 1 month after surgery (U=6.045,P＜0.05).Preoperatively,there were no significant differences in the release rate of all tear cytokines between the two groups.At 2 hours postoperatively,the mean release rates of IL-8 and TNFα in the off-flap group were significantly lower than those in the on-flap group (Z=-1.965,-2.145,P＜0.05).On postoperative days 1 and 5,no significant differences were observed in the release rate of all cytokines between the 2 groups.Conclusion Off-flap Epi-LASIK offers faster corneal epithelial healing and visual recovery,and temporarily less haze than from on-flap Epi-LASIK.The lower tear levels of IL-8 and TNFα in the off-flap group 2 hours after surgery may suggest a possible mechanism for the clinical differences. Key words: Keratomileusis,laser in situ ; Myopia; Inflammatory cytokine; Tear