Confocal microscopy evaluations of the effect of contact lens wearing on corneal reinnervation before and after SBK

Objective To analyze the effect of contact lens (CL) wear on corneal reinnervation after sub-Bowman keratomileusis (SBK) corneal subbasal nerve fibers (CSNFs) by in vivo confocal microscopy (IVCM) and to evaluate the clinical applications of IVCM on corneal reinnervation.Methods It was a prospective cohort study.Forty-three patients (86 eyes) were selected from May 2010 to June 2011 in Beijing Tongren Eye Center.The age was 18-35 years old,refractive errorwas-2.75--10.00 D.They were divided into 4 groups:group I,time of soft CL wearing ≤5 years (20 eyes); group Ⅱ,5 years＜time of soft CL wearing≤10 years (12 eyes); Group Ⅲ,time of soft CL wearing ＞10 years (8 eyes); group Ⅳ,without history of CL wearing (46 eyes).The density,number,tortuosity and regenerated velocity of CSNFs of different group were evaluated by IVCM before and 1,3,6 months after SBK.Data were analyzed with independent t test,one-factor analysis of variance and chi-square test.Results There were no significant difference of density,number and tortuosity of central CSNFs among different groups preoperative (F=1.042,1.947,0.821,P＞0.05),but the density and number of central CSNFs decrcased and the tortuosity increased in group of CL wearing ＞10 years.The density and number of central CSNFs were significant lower,and the tortuosity was significant higher than that of pre-operation (t=6.150,-4.141,9.709,P＜0.01).The density,number and tortuosity of central CSNFs among different groups were not significant different (F=1.472,0.318,0.353,P＞0.05),but the longer CL wearing,the lower density and number of central CSNFs and the higher tortuosity were.The velocity of CSNFs regeneration among different groups were not significant different (x2=4.273,8.806,5.364,P＞0.05),but the percentage of regenerated CSNFs deriving into the central 3 mm in group Ⅲ was lower than other groups at 3 and 6 month after surgery.Conclusion The time of CL wearing has no significant effect on CSNFs reinnervation before and after SBK.But long time wearing would delay the reinnervation of CSNFs.IVCM was useful to quantitative evaluate the corneal reinnervation pre-SBK and post-SBK. Key words: Microscopy,confocal;  Keratomileusis, sub-Bowman ;  Contact lenses ;  Subbasal nerve fibers,corneal