Incidence of elderly eye injuries in automobile crashes: the effects of lens stiffness as a function of age.

The purpose of this paper is to elucidate the incidence of eye injuries with respect to occupant age in frontal automobile crashes as well as to investigate possible injury mechanisms of the elderly eye and the effects of lens stiffness. The National Automotive Sampling System was searched from years 1993-2000 for three separate occupant age groups of 16-35 years old, 36-65 years old, and 66 years old and greater in order to compare the total number of weighted occupants who sustained an eye injury to the number of occupants who sustained an eye injury per age group. Three separate impact scenarios simulating a foam particle (30 m/s), a steering wheel (15 m/s), and an air bag (67 m/s), were applied to a finite element eye model in order to elucidate the effects of aging on the eye when subjected to blunt trauma. The lens stiffness of the model was varied according to human lens stiffness values determined for each age group. Occupants aged 66 years old and greater were two to three times more likely to incur an eye injury than younger occupants. The computational eye model demonstrated that increased risk was related to the increasing stiffness of the lens, producing up to a 120% larger stress in the ciliary body.