兔眼准分子激光原位角膜磨镶术后角膜扩张的研究

The Research of Post-LASIK Keratectasia in Rabbits' Eyes after LASIK Surgery

在离体状态下研究兔眼角膜在不同厚度与眼压下的前凸变化。健康新西兰大白兔30眼,分成3组,1组:对照组,未切削眼;2组:切削原角膜厚度的1/3,3组:切削原角膜厚度的1/2。固定角膜并对角膜内表面加压。利用三维激光扫描仪测量不同压力下各角膜前凸位移量,并对其进行方差分析;建立正常兔眼角膜有限元模型,由实验数据反推弹性模量,并分析各组模型的Mise应力分布。结果表明:低压下,第3组与1、2组比较,差异均有统计学意义(P<0.05);弹性模量随切削量的增加而增加;应力分布变化与角膜厚度相关。说明:准分子激光术后的角膜扩张与角膜力学性能的改变有关。角膜扩张与厚度有关,角膜厚度变薄到一定程度,角膜前凸明显,1/2厚度可能是临界值。因此,准分子激光原位角膜磨镶术预留剩余角膜基质床的厚度不小于原始角膜厚度的1/2较安全,同时应将眼压维持在相对较低的水平。

To research the rabbit corneal protrusion after excimer laser incision ex vivo. To study the relation among the rabbit corneal protrusion , the central corneal thickness and the intraocttlar pressure. Thirty eyes of fifteen New Zealand rabbits were divided into three groups in the study- teneyes were incised 1/3 primitive corneal thickness with excimer laser and other ten eyes were incised 1/2, the rest ten were controlled; the 3D laser scanner was used to measure the pre - set corneal sample in different pressure. The corneal protrusion changes was converted into logarithm and evaluated in variance analysis. Finally, the corneal elastic modttlus of rabbit with accessed protrusive displacement was calcttlated using abaqns finite element software. Result showed that the group of 1/2 ablation, normal group and the group of 1/3 ablation under same pressures were statistically meaningfttl. With increasing keratectomy volume, the corneal elastic modulus of rabbit was calculated and stress was increased. It proves that the change of corneal biomechanical property has some relationship with post - LASIK keratectasia . The post - LASIK keratectasia has some relationship with thickness and pressure. The corneal protrusion of group of 1/2 ablation is obvious. To insure the stability and security of LASIK, the residual corneal stroma- bed thickness must be more than haft of primary thickness and intraocttlar pressure（IOP） should be maintained at the lower level in normal lOP.