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J Mech Behav Biomed Mater. 2018 Jul;83:126-134. doi: 10.1016/j.jmbbm.2018.04.016. Epub 2018 Apr 19.

Development and clinical verification of numerical simulation for laser in situ keratomileusis.

Author information

1
Eye Hospital, WenZhou Medical University, Wenzhou 325027, China; The institution of ocular biomechanics, Wenzhou Medical University, Wenzhou, Zhejiang Province 325027, China.
2
Eye Hospital, WenZhou Medical University, Wenzhou 325027, China.
3
Eye Hospital, WenZhou Medical University, Wenzhou 325027, China. Electronic address: chenle@rocketmail.com.
4
Eye Hospital, WenZhou Medical University, Wenzhou 325027, China; The institution of ocular biomechanics, Wenzhou Medical University, Wenzhou, Zhejiang Province 325027, China. Electronic address: wangqm55@126.com.
5
School of Engineering, University of Liverpool, Liverpool L69 3GH, UK; National Institute for Health Research (NIHR) Biomedical Research Centre for Ophthalmology, Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London, UK.

Abstract

To develop and validate numerical models of the laser in situ keratomileusis (LASIK) procedure through considering its effect on corneal biomechanical behavior. 3D finite element models of the human eye were developed to simulate LASIK. The models' predictions of post-operative corneal elevation, corneal refractive power with vector decomposition (M-c-pos, J0-c-pos, J45-c-pos) and refractive error correction (M-rec, J0-rec, J45-rec) were compared against clinical data obtained for 28 eyes of 28 patients. A parallel exercise was conducted to estimate the post-operative corneal shape using a shape subtraction method (SSM) - which does not consider the effects of LASIK on corneal mechanical behavior - and the results are compared with the finite element method (FEM). A significant decrease in elevation differences between FEM predictions and clinical data was found compared with the differences between SSM results and clinical data (p = 0.000). In addition, there were no significant differences in post-operative equivalent sperical corneal refractive power between FEM results and corresponding clinical data (M-c-pos: p = 0.501), while SSM showed significant differences with clinical data (M-c-pos: p = 0.000). Further, FEM achieved a predicted value of M-c-pos within ± 1.00D accuracy in 100% of cases, compared with 57% achieved by the SSM. M-rec predicted by FEM was not significantly different from clinical results (p = 0.085), while SSM overestimated it (p = 0.000). The match between LASIK numerical model predictions with clinical measurements improved significantly when the procedure's effect on corneal biomechanical behavior was considered. This outcome has important implications on efforts to develop planning tools for refractive surgery.

KEYWORDS:

Corneal refractive surgery; Finite element simulation; Myopic correction; Ocular biomechanics

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