Simulation of air-bag impact on post-radial keratotomy eye using finite element analysis

Purpose: To determine the physical and mechanical conditions of an impactin g air bag that causes corneal rupture in a post-radial keratotomy (RK eye u sing a simulation model of the human eye. Setting: Numerical simulation study on a computer. Methods: The simulations were performed by a computer using the finite elem ent analysis program PAM-CRASH (Nihon ESI). The air bag was set to impact t he surface of a post-RK eye with 4, 6, or 8 corneal incisions at various ve locities. Strain on the corneal tissue including scarred incisions exceedin g 9.0% was assumed to indicate the possibility of corneal rupture. Results: At a medium velocity of 30 m/s, corneal rupture was likely to occu r. At an air-bag impact velocity of 40 m/s, 3 of 4, 5 of 6, and 8 of 8 inci sions were likely to rupture in the case of 4-, 6-, and 8-incision procedur es, respectively, leading to likely globe rupture in all situations. Lacera tions extended beyond the incisions and involved the intact cornea at a vel ocity of 40 m/s. If the corneal tissue strength reduction was increased to 90%, most incisions were likely to rupture at impact velocities greater tha n 35 m/s in all incision procedures. Conclusions: The results could partly reflect a reported case of globe rupt ure after RK and suggest that severe ocular trauma can be caused in the pos t-RK eye by air bags at ordinary impact velocities. (C) 2001 ASCRS and ESCR S.