LASIK手术剩余基质床厚度安全保留值的数值模拟研究
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1.四川大学;2.太原理工大学

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基金项目:

四川省国际合作项目(2018HH0073)


Research on Numerical Simulation of the Safe Retention Value of RSBT in LASIK
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Affiliation:

1.Sichuan University;2.Taiyuan University of technology

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International Cooperation Programs of Science & Technology Department of Sichuan Province

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    摘要:

    目的 准分子激光原位角膜磨镶术(Laser-assisted in situ keratomileusis, LASIK)已广泛应用于临床近视矫正,其安全性、准确性、稳定性获得了医生和患者的认可,但其剩余基质床厚度(residual stromal bed thickness,RSBT)安全保留值一直未得到统一的结论,学界主要争论在250μm、280μm和300μm。本文主要应用有限元方法,依靠力学手段,研究角膜生物力学特性。文中分析了LASIK手术不同RSBT在不同眼压下对角膜几何变形和应力变化的影响,并结合医学研究成果,利用力学分析手段,评估这三种RSBT保留值的安全性。方法 利用ABAQUS有限元软件建立了正常角膜与术后不同RSBT的角膜的有限元模型,设置合适的加载与边界条件,计算得出相应的位移与应力。结果 角膜前表面顶点位移的模拟结果显示, RSBT=250μm的术后角膜在IOP=20mmHg的作用下和正常角膜IOP=40mmHg的作用下产生的顶点位移基本相等;角膜前表面中央平均曲率半径的结果中,RSBT=280μm处于圆锥角膜发病低危区,而RSBT=250μm已经进入高危区;角膜前后表面中心张应力的模拟结果表明,在RSBT为280μm和300μm之间某值,应力分布规律与正常角膜基本一致,根据角膜组织学研究,RSBT=300μm时,角膜基质层的张应力强度丧失约40%。结论 RSBT=300μm为LASIK手术比较合理的最低保留值,RSBT=250μm是高风险值,在RSBT=330~340μm时,即对大部分患者来说,LASIK手术是足够安全的。

    Abstract:

    Objective Laser-assisted in situ keratomileusis (LASIK) has been widely used in clinical correction of myopia, and its safety, accuracy and stability have been recognized by doctors and patients. Some researchers thought RSBT=300μm is safe, while others thought 280μm or 250μm is safe. In this paper, the biomechanical properties of cornea were studied by using finite element method and mechanical means. We analyzed the effects of different RSBT in LASIK surgery on the geometric deformation and stress changes of the cornea under different intraocular pressures (IOP), and evaluated its safety to obtain the minimum retention value, which will provide a mechanical reference for clinical surgery practice and medical statistical research. Method The finite element software ABAQUS was used to conduct the modeling of a normal cornea and corneas of different RSBT after surgery. Appropriate loading and boundary conditions were set and then the results about displacement and stress were calculated. Results The results about apical displacement of the anterior corneal surface indicate that the apical displacement of the postoperative cornea (RSBT=250μm) under IOP=20mmHg is the same as that of the normal cornea (RSBT=550μm) under IOP=40mmHg; According to the results about the mean radius of curvature of the anterior and posterior central surface of corneas, RSBT=280μm is in the low risk area of keratoconus, while RSBT=250μm has been in the high-risk area; The results about central tensile stress on the anterior and posterior corneal surface indicate that, at a value between 280μm and 300μm of RSBT, the stress distribution is nearly consistent with that of the normal cornea. According to the study of corneal histology, when RSBT=300μm, the stromal layer of the cornea lost the first 40% of the strongest strength against tissue tension. Conclusions RSBT=250μm is the minimum retention value for LASIK surgery; RSBT=250μm is the high risk value; When RSBT=330~340μm, that is, for most patients, LASIK surgery is safe enough.

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  • 收稿日期:2019-10-14
  • 最后修改日期:2019-12-18
  • 录用日期:2019-12-31
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