Simulation of airbag impact on eyes after photorefractive keratectomy by finite element analysis method

BACKGROUND: A simulation model of the human eye which we have developed was applied to simulated airbag ocular injury, to determine the physical and mechanical conditions of the impacting airbag that would cause globe rupture in a post-photorefractive keratectomy (PRK) eye. METHODS: Simulations were performed with a computer using the finite element analysis program PAM-CRASH()(Nihon ESI, Tokyo, Japan). The airbag was set to impact on the surface of post-PRK eyes-D3, D6, D10, and D15-and an intact eye at various impact velocities. Strain on the cornea and sclera exceeding 18.0% and 6.8%, respectively, was assumed to indicate the possibility of rupture of each tissue. RESULTS: In contrast to the intact eye, in post-PRK eyes, at the lowest velocity of 20 m/s, some of the element reached the strain threshold in D15. At the medium velocity of 30 m/s, limited corneal rupture was observed in all situations. At the high velocity, 40 m/s, scleral laceration was found in eyes with all diopters, and apparent corneal rupture was observed in D10 and D15, indicating that globe rupture was very likely to occur. CONCLUSION: These results suggest that severe ocular trauma can be caused in post-PRK eyes by airbags at high impact velocities. Preoperative discussion with candidates for laser refractive surgery regarding the potential for severe ocular injury if the normal integrity of the eye is compromised by surgery may be appropriate. Research on modification of airbag design and deployment to minimize the risk of ocular injury is important.