{"title":"Safety evaluation after LASIK surgery based on the linear creep property: a finite element analysis.","authors":"Ji-Xi Guo, Xue-Feng Li, Xin-Chao Wang, Xin-Heng Zhao, Yan Wang, Li-Hua Fang","doi":"10.18240/ijo.2025.05.15","DOIUrl":null,"url":null,"abstract":"<p><strong>Aim: </strong>To investigate the effect of the percent tissue altered (PTA) on the safety after laser-assisted <i>in situ</i> keratomileusis (LASIK) based on linear creep characteristics.</p><p><strong>Methods: </strong>The linear creep characteristics of the cornea were characterized by the generalized Kelvin-Voigt constitutive relationship with five parameters. Then, the displacement and stress distribution on the anterior and posterior surfaces of the cornea were analyzed by constructing the eye model with different PTA.</p><p><strong>Results: </strong>When PTA was above 39%, the vertex displacements under physiological intraocular pressure (IOP, 15 mm Hg) exceeded that of the preoperative glaucoma under average IOP. That is, an excessively high displacement value was found. In addition, with the increase of PTA, the central cornea was stretched thinner and more obviously due to IOP. When PTA was above 39%, the stress at the center of the anterior surface of the residual stroma was more than 20% larger than that of the normal human eye. The residual stroma was forced to stretch more severely due to excessive stress on the anterior surface. This resulted in deformation of the stroma and induced corneal ectasia. Meanwhile, the postoperative vertex displacement increased with the decrease in viscosity ratio.</p><p><strong>Conclusion: </strong>PTA less than 39% is the safe range for LASIK surgery. This study may provide a reliable numerical basis for postoperative corneal dilatation and the outcomes after refractive surgery.</p>","PeriodicalId":14312,"journal":{"name":"International journal of ophthalmology","volume":"18 5","pages":"889-896"},"PeriodicalIF":1.9000,"publicationDate":"2025-05-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12043300/pdf/","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"International journal of ophthalmology","FirstCategoryId":"3","ListUrlMain":"https://doi.org/10.18240/ijo.2025.05.15","RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"2025/1/1 0:00:00","PubModel":"eCollection","JCR":"Q2","JCRName":"OPHTHALMOLOGY","Score":null,"Total":0}
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Abstract
Aim: To investigate the effect of the percent tissue altered (PTA) on the safety after laser-assisted in situ keratomileusis (LASIK) based on linear creep characteristics.
Methods: The linear creep characteristics of the cornea were characterized by the generalized Kelvin-Voigt constitutive relationship with five parameters. Then, the displacement and stress distribution on the anterior and posterior surfaces of the cornea were analyzed by constructing the eye model with different PTA.
Results: When PTA was above 39%, the vertex displacements under physiological intraocular pressure (IOP, 15 mm Hg) exceeded that of the preoperative glaucoma under average IOP. That is, an excessively high displacement value was found. In addition, with the increase of PTA, the central cornea was stretched thinner and more obviously due to IOP. When PTA was above 39%, the stress at the center of the anterior surface of the residual stroma was more than 20% larger than that of the normal human eye. The residual stroma was forced to stretch more severely due to excessive stress on the anterior surface. This resulted in deformation of the stroma and induced corneal ectasia. Meanwhile, the postoperative vertex displacement increased with the decrease in viscosity ratio.
Conclusion: PTA less than 39% is the safe range for LASIK surgery. This study may provide a reliable numerical basis for postoperative corneal dilatation and the outcomes after refractive surgery.
目的：探讨基于线性蠕变特征的组织改变率（PTA）对激光原位角膜磨圆术（LASIK）术后安全性的影响。方法：采用具有5个参数的广义Kelvin-Voigt本构关系表征角膜的线性蠕变特性。然后，通过构建不同PTA的眼模型，分析角膜前后表面的位移和应力分布。结果：当PTA高于39%时，生理眼压（IOP, 15 mm Hg）下的青光眼顶点位移大于术前平均眼压下的青光眼。即发现了过高的位移值。此外，随着PTA的增加，中央角膜因IOP而被拉伸的更薄、更明显。当PTA大于39%时，残余间质前表面中心应力比正常人大20%以上。由于前表面的过度应力，残余间质被迫更严重地拉伸。这导致基质变形和角膜扩张。同时，术后顶点位移随黏度比的减小而增大。结论：PTA小于39%是LASIK手术的安全范围。本研究可为术后角膜扩张及屈光手术结果提供可靠的数值依据。
期刊介绍：
· International Journal of Ophthalmology-IJO (English edition) is a global ophthalmological scientific publication
and a peer-reviewed open access periodical (ISSN 2222-3959 print, ISSN 2227-4898 online).
This journal is sponsored by Chinese Medical Association Xi’an Branch and obtains guidance and support from
WHO and ICO (International Council of Ophthalmology). It has been indexed in SCIE, PubMed,
PubMed-Central, Chemical Abstracts, Scopus, EMBASE , and DOAJ. IJO JCR IF in 2017 is 1.166.
IJO was established in 2008, with editorial office in Xi’an, China. It is a monthly publication. General Scientific
Advisors include Prof. Hugh Taylor (President of ICO); Prof.Bruce Spivey (Immediate Past President of ICO);
Prof.Mark Tso (Ex-Vice President of ICO) and Prof.Daiming Fan (Academician and Vice President,
Chinese Academy of Engineering.
International Scientific Advisors include Prof. Serge Resnikoff (WHO Senior Speciatist for Prevention of
blindness), Prof. Chi-Chao Chan (National Eye Institute, USA) and Prof. Richard L Abbott (Ex-President of
AAO/PAAO) et al.
Honorary Editors-in-Chief: Prof. Li-Xin Xie(Academician of Chinese Academy of
Engineering/Honorary President of Chinese Ophthalmological Society); Prof. Dennis Lam (President of APAO) and
Prof. Xiao-Xin Li (Ex-President of Chinese Ophthalmological Society).
Chief Editor: Prof. Xiu-Wen Hu (President of IJO Press).
Editors-in-Chief: Prof. Yan-Nian Hui (Ex-Director, Eye Institute of Chinese PLA) and
Prof. George Chiou (Founding chief editor of Journal of Ocular Pharmacology & Therapeutics).
Associate Editors-in-Chief include:
Prof. Ning-Li Wang (President Elect of APAO);
Prof. Ke Yao (President of Chinese Ophthalmological Society) ;
Prof.William Smiddy (Bascom Palmer Eye instituteUSA) ;
Prof.Joel Schuman (President of Association of University Professors of Ophthalmology,USA);
Prof.Yizhi Liu (Vice President of Chinese Ophtlalmology Society);
Prof.Yu-Sheng Wang (Director of Eye Institute of Chinese PLA);
Prof.Ling-Yun Cheng (Director of Ocular Pharmacology, Shiley Eye Center, USA).
IJO accepts contributions in English from all over the world. It includes mainly original articles and review articles,
both basic and clinical papers.
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