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Finite Element Analysis of Changes in Tensile Strain by Airsoft Gun Impact on Eye and Deformation Rate in Eyes of Various Axial Lengths

Authors Takahashi R, Okamura K, Tsukahara-Kawamura T, Harada K, Saeki Y, Ozaki H, Uchio E

Received 12 February 2020

Accepted for publication 28 April 2020

Published 26 May 2020 Volume 2020:14 Pages 1445—1450

DOI https://doi.org/10.2147/OPTH.S249483

Checked for plagiarism Yes

Review by Single-blind

Peer reviewer comments 2

Editor who approved publication: Dr Scott Fraser


Rie Takahashi, Kanno Okamura, Tomoko Tsukahara-Kawamura, Kazuhiro Harada, Yusuke Saeki, Hiroaki Ozaki, Eiichi Uchio

Department of Ophthalmology, Fukuoka University School of Medicine, Fukuoka, Japan

Correspondence: Eiichi Uchio
Department of Ophthalmology, Fukuoka University School of Medicine, 7-45-1 Nanakuma, Fukuoka, Jonan-Ku 814-0180, Japan
Tel +81 92 801 1011
Fax +81 92 865 4445
Email euchio@fukuoka-u.ac.jp

Purpose: We have carried out three-dimensional finite element analysis (FEA) to determine the physical and mechanical response in several ocular injuries. We applied this FEA model to evaluate an airsoft gun impact on an eye and the deformation rate of eyes of various axial lengths at various velocities.
Methods: This study was carried out on a human eye model using an FEA program created by Nihon, ESI Group. The airsoft gun pellet was set to impact the eye at initial velocities of 45, 60 and 75 m/s with the addition of variation in axial length of 20 mm (hyperopia), 22 mm (emmetropia), 24 mm (myopia) and 26 mm (high myopia). Deformation of the eye was calculated as the decrease rate of the volume of the eyeball and the decrease rate of the axial length.
Results: In all emmetropic cases, the cornea reached its strain threshold during the impact, and scleral strain showed a patchy strength distribution in the simulation. The deformation was most evident in the anterior segment, while deformation of the posterior segment was less. The decrease rate of the volume of the eyeball and decrease rate of the axial length were highest in the hyperopic eye, followed by the emmetropic eye and myopic eye, and the high myopic eye showed the lowest decrease rates among the four axial lengths in all impact velocity simulations.
Conclusion: These results suggest that hyperopic eyes are most susceptible to deformation by an airsoft gun impact compared with other axial length eye models in this simulation. The considerable deformation by an airsoft gun impact shown in this study might indicate the necessity of ocular protection to avoid permanent eye injury. FEA using a human eyeball model might be a useful method to analyze and predict the mechanical features of ocular injury by an airsoft gun.

Keywords: airsoft gun, finite element analysis, globe, cornea, rupture, deformation

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