目的:评估将两种常见的激光视力矫正程序(tPRK和FS-LASIK)与交联(在tPRKXtra和FS-LASIKXtra中)结合使用时,有术后扩张风险的患者角膜生物力学的变化。方法:该研究包括143只近视的143只眼,将散光患者分为非交联屈光手术组(非Xtra组,tPRK和FS-LASIK)和交联组(Xtra组,tPRKXtra和FS-LASIKXtra)根据扩张症风险评分系统。对眼睛进行测量,包括应力-应变指数(SSI),首次压平时的刚度参数(SP-A1),积分反半径(IIR),顶点处的变形幅度(DA),顶点与距顶点2mm的变形幅度之比(DARatio2mm)。术前和术后1、3和6个月进行测量(pos1m,POS3M,和pos6m)。在pos1m处记录到内皮(PDLD)和消融表面(DLA)的后分界线深度。结果:SP-A1明显下降,而IIR,变形幅度,所有四组术后DARatio2mm均显着增加(p<0.01)-均表示刚度降低。在FS-LASIK组中,IIR的变化,DA,DARatio2mm为32.7±15.1%,12.9±7.1%,分别为27.2±12.0%,与20.1±12.8%相比,显著更高(p<0.05),6.4±8.2%,FS-LASIKXtra组为19.7±10.4%。在tPRK组中,IIR的变化为27.3±15.5%,显著大于tPRKXtra组的16.9±13.4%。在tPRK中,SSI的变化很小(-1.5±21.7%,p=1.000),tPRKXtra(8.4±17.9%,p=0.053),和FS-LASIKXtra(5.6±12.7%,p=0.634)组,但在FS-LASIK组中显著(-12.1±7.9%,p<0.01)。校正基线生物力学指标后,术前bIOP和中央角膜厚度(△CCT)从pre到pos6m的变化,FS-LASIK和tPRK组IIR的变化,以及DA,FS-LASIK组的DARatio2mm和SSI在统计学上仍高于其相应的Xtra组(均p<0.05)。最重要的是,在校正这些协变量后,FS-LASIKXtra中DARatio2mm的变化在统计学上小于tPRKXtra(p=0.017).结论:统计分析结果表明,tPRKXtra和FS-LASIKXtra可有效减少屈光手术(tPRK和FS-LASIK)引起的生物力学损失。FS-LASIK的角膜整体硬度下降幅度大于tPRK,LASIK术后CXL的生物力学增强也高于tPRK。
Purpose: To evaluate the change in corneal biomechanics in patients with postoperative ectasia risk when combining two common laser vision correction procedures (tPRK and FS-LASIK) with cross-linking (in tPRK Xtra and FS-LASIK Xtra). Methods: The study included 143 eyes of 143 myopic, astigmatic patients that were divided into non-cross-linked refractive surgery groups (non-Xtra groups, tPRK and FS-LASIK) and cross-linked groups (Xtra groups, tPRK Xtra and FS-LASIK Xtra) according to an ectasia risk scoring system. The eyes were subjected to measurements including the stress-strain index (SSI), the stiffness parameter at first applanation (SP-A1), the integrated inverse radius (IIR), the deformation amplitude at apex (DA), and the ratio of deformation amplitude between apex and 2 mm from apex (DARatio2mm). The measurements were taken preoperatively and at 1, 3, and 6 months postoperatively (pos1m, pos3m, and pos6m). Posterior demarcation line depth from the endothelium (PDLD) and from the ablation surface (DLA) were recorded at pos1m. Results: SP-A1 significantly decreased, while IIR, deformation amplitude, and DARatio2mm increased significantly postoperatively in all four groups (p < 0.01)-all denoting stiffness decreases. In the FS-LASIK group, the changes in IIR, DA, and DARatio2mm were 32.7 ± 15.1%, 12.9 ± 7.1%, and 27.2 ± 12.0% respectively, which were significantly higher (p < 0.05) compared to 20.1 ± 12.8%, 6.4 ± 8.2%, and 19.7 ± 10.4% in the FS-LASIK Xtra group. In the tPRK group, the change in IIR was 27.3 ± 15.5%, significantly larger than 16.9 ± 13.4% in the tPRK Xtra group. The changes of SSI were minimal in the tPRK (-1.5 ± 21.7%, p = 1.000), tPRK Xtra (8.4 ± 17.9%, p = 0.053), and FS-LASIK Xtra (5.6 ± 12.7%, p = 0.634) groups, but was significant in the FS-LASIK group (-12.1 ± 7.9%, p < 0.01). After correcting for baseline biomechanical metrics, preoperative bIOP and the change in central corneal thickness (△CCT) from pre to pos6m, the changes in the IIR in both FS-LASIK and tPRK groups, as well as DA, DARatio2mm and SSI in the FS-LASIK group remained statistically greater than their corresponding Xtra groups (all p < 0.05). Most importantly, after correcting for these covariates, the changes in DARatio2mm in the FS-LASIK Xtra became statistically smaller than in the tPRK Xtra (p = 0.017). Conclusion: The statistical analysis results indicate that tPRK Xtra and FS-LASIK Xtra effectively reduced the biomechanical losses caused by refractive surgery (tPRK and FS-LASIK). The decrease in corneal overall stiffness was greater in FS-LASIK than in tPRK, and the biomechanical enhancement of
CXL was also higher following LASIK than after tPRK.