兔LASIK术后角膜瓣弃留与紫外线照射对角膜上皮下雾状混浊影响的实验研究

Effects of preserving or removing corneal flap and UV-B irradiation on haze formation after LASIK surgery in rabbit

目的了解LASIK术后角膜瓣存在与丢失情况下紫外线对角膜上皮下雾状混浊(Haze)的影响。方法 36只新西兰大耳白兔随机编号分为Ⅰa组、Ⅰb组、Ⅰc组、Ⅱa组、Ⅱb组及Ⅱc组6组,每组6只,取Ⅰa组、Ⅰb组、Ⅱa组及Ⅱb组共24只兔双眼按LASIK术式制作角膜瓣(Ⅰc组和Ⅱc组为对照组),术后即刻人为去除Ⅰb组及Ⅱb组双眼角膜瓣,术后1周Ⅰa组、Ⅰb组及Ⅰc组行紫外线照射7min(100mJ.cm-2,UV-B灯照射),术后裂隙灯观察并记录Haze等情况,分别于术后3周及5周每组取3只兔角膜行HE染色光镜检查及透射电镜检查。结果术后Ⅰa组、Ⅱa组、Ⅰb组、Ⅱb组角膜上皮愈合时间分别为(0.6583±0.1379)d、(0.7417±0.1832)d、(2.9667±0.4997)d、(2.8167±0.4152)d,经统计学处理,Ⅰa组与Ⅱa组、Ⅰb组与Ⅱb组之间差异均无统计学意义(均为P>0.05),Ⅰa组与Ⅰb组、Ⅰa组与Ⅱb组、Ⅱa组与Ⅰb组及Ⅱa组与Ⅱb组之间差异均有统计学意义(均为P<0.05)。术后1周,Ⅰb组及Ⅱb组24眼皆有Haze发生,Haze程度为1～2级,且术后3周和5周时,Ⅰb组Hzae程度较Ⅱb组重,差异均有统计学意义(均为P<0.05);Ⅰa组、Ⅱa组、Ⅰc组及Ⅱc组角膜透明,无Haze发生。Ⅰa组、Ⅱa组、Ⅰc组及Ⅱc组光镜及电镜下未见明显异常。Ⅱb组光镜下可见3周时角膜上皮细胞增生,上皮细胞排列紊乱、连接稍疏松,少数细胞空泡变,上皮和基质层存在散在裂隙;Ⅰb组与之病变相似,但更为严重,且5周时2组病变均逐渐加重。透射电镜下3周时可见,Ⅱb组上皮基底细胞的半桥粒稀疏、基底膜不连续、厚薄不均匀,基质浅层胶原纤维排列紊乱,胶原纤维之间间隔不规则,成纤维细胞极度活化,数量增多,胞质内细胞器增多;Ⅰb组与之病变相似,但更为严重,且5周时2组病变均较3周时加重。结论 LASIK术后角膜瓣的丢失引起术后Haze的发生,紫外线照射加重角膜组织的损害、增加Haze的发生率,而完整角膜瓣的存在,可以减少紫外线对角膜组织的损害,降低Haze的发生率。

Objeetive To investigate the effects of UV-B irradiation on haze for- mation under the condition of preserving or removing corneal flap. Methods Thirty- six New Zealand white rabbits were divided randomly into group I a, I b, I c, II a, IIb and IIc,6 cases in each group. The corneal flap in 24 rabbits of group I a, I b, IIa and IIb were made by LASIK, group I c and II c were set as control, and the corneal flap of dual eyes in group I b and group IIb were removed immediately after LASIK. One week after operation, rabbits in group I a, I b and I c were exposed to UV-B （100 mJ · cm-2 ） for 7 minutes. The haze was observed and evaluated after operation and UV-B irradiation. HE staining and transmission electron microscopy were performed at 3 weeks and 5 weeks after operation in 3 rabbits of each group. Results The curing times of corneal epithelium were（0. 658 3±0. 137 9） days, （0. 741 7 ±0. 183 2） days, （2.965 7 ± 0.499 7） days and（2.816 7 ±0.415 2） days in group I a, IIa, [ b and lib,respectively, there was no statistical difference between group I a and II a, group I b and II b （ both P 〉 0.05 ）, but there were statistical differences between other two groups （ both P 〈 0. 05 ）. At l week after operation, haze appeared in both 24 eyes of group I b and IIb with grade 1 to 2. At 3 weeks and 5 weeks after operation,haze in group I b was seve- rer than that in group II b, there were statistical differences （ both P 〈 0.05 ） ; No haze formed in group I a, II a, I c and II c with no abnormal under light microscope and electron microscope. At 3 weeks, the hyperplasia, disorganization and connected porosity of corneal endothelial cells with a little cell vacuolization and gap were presented in group IIb under light microscope. The conditions severer than that described as above also were found in group I b. In the meantime, the situations of group II b and I b worsened at 5 weeks after operation. The images under transmission electron micro- scope showed scattering hemldesmosome of epithelia cells of basal layer, nonsequenees of basement membrane, uneven thickness, disarranged collagen fibers of superficial stroma,irregular interval between collagen fibers, excessive activation and hyperplasia of fibroblasts and cytoplasm organelles increase in group II b and I b, especially in the latter. Furthermore, the circumstances of group II b and group I b deteriorated at 5 weeks. Conclusion Removing the corneal flap after LASIK can induce the haze for- mation,and UV-B irradiation will aggravate the damage of corneal tissue and increase the haze formation,while preserving the corneal flap can reduce the damages of UV-B irradiation on corneal tissue and decrease the haze formation.