<p>Finite Element Analysis of Air Gun Impact on Post-Keratoplasty Eye</p>

Abstract

Due to the mechanical vulnerability of eyes that have undergone penetrating keratoplasty (PKP), it is clinically important to evaluate the possibility of corneal wound dehiscence by blunt impact. We have previously developed a simulation model resembling a human eye based on information obtained from cadaver eyes and applied three-dimensional finite element analysis (FEA) to determine the physical and mechanical response to an air gun impact at various velocities on the post-PKP eye. Methods: Simulations in a human eye model were performed with a computer using a FEA program created by Nihon, ESI Group. The air gun pellet was set to impact the eye at three-different velocities in straight or 12°up-gaze positions with the addition of variation in keratoplasty suture strength of 30%, 50% and 100% of normal corneal strength. Results: Furthermore to little damage in the case of 100% strength, in cases of lower strength in a straight-gaze position, wound rupture seemed to occur in the early phase (0.04-0.06 ms) of impact at low velocities, while regional break was observed at 0.14 ms after an impact at high velocity (75 m/s). In contrast, wound damage was observed in the lower quadrant of the suture zone and sclera in 12°up-gaze cases. Wound damage was observed 0.08 ms after an impact threatening corneoscleral laceration, and the involved area being larger in middle impact velocity (60 m/s) simulations than in lower impact velocity simulations, and larger damaged area was observed in high impact velocity cases and leading to corneoscleral laceration. Conclusion: These results suggest that the eye is most susceptible to corneal damage around the suture area especially with a straight-gaze impact by an air gun, and that special precautionary measures should be considered in patients who undergo PKP. FEA using a human eyeball model might be a useful method to analyze and predict the mechanical features of eyes that undergo keratoplasty.

Finite Element Analysis of Changes in Deformation of Intraocular Segments by Airbag Impact in Eyes of Various Axial Lengths

“… 32 Vitreous was modeled as a solid mass with a hydrostatic pressure of 20 mmHg (2.7 kPa). 37 , 38 To our knowledge, there are no published data on the mechanical properties, especially on the tensile strength, of the zonule of Zinn, and thus, the suspensory ligaments and ciliary muscles are not included in this model. The elastic properties and meshing principles of the model human normal eye (emmetropia) were similar to those in previous reports.…”

“…32 This model human eye was also used in our studies on airbag impact in various situations. [33][34][35][36][37][38] We applied this FEA model and reported that considerable damage was observed especially at higher impact velocities, such as 50 or 60 m/s, in eyes with any axial length, and deformation was most evident in the anterior segment. 39 In these studies, we mainly reported mechanical damage of the ocular surface, such as laceration, perforation, etc., and deformation of the whole eyeball was evaluated, but intraocular deformation, which is closely related to angle recession, lens rupture and vitreous traction etc., was not evaluated.…”

Simulation of Changes in Tensile Strain by Airbag Impact on Eyes After Trabeculectomy by Using Finite Element Analysis

“…22 We have previously developed a simulation model resembling a human eye 23 and applied three-dimensional FEA to determine the physical and mechanical response of the eyeball to an impacting airbag or airsoft gun projectile. [24][25][26][27][28][29][30] The important benefits of computer models to analyze biomechanical experiments and to quantify mechanical parameters are that we can evaluate the tensile strain of ocular segments by freely changing the impacting velocity or ocular tissue properties and they may reduce the need for animal studies, which are being increasingly restricted on ethical grounds.…”

Finite element analysis of changes in tensile strain and deformation by airbag impact in eyes of various axial lengths

“…Therefore, we planned to study the kinetic phenomenon of an airbag impact on a human eye using a FEA method, which was also applied in several of our previous studies on other types of injury than airbag injury [ 23 , 24 ]. If we were able to reproduce the kinetic phenomena including intraocular deformation caused by an airbag impact sequentially, this would increase understanding of the pathophysiological mechanism of blunt ocular trauma by an airbag.…”