The effects of extraocular muscles on static displacements of the human eye

More than 30,000 people lose sight in at least one eye every year in the United States. Globe rupture is one of the most severe injuries and can often result in the loss of an eye. Previous studies to determine the injury tolerance of the human eye to globe rupture have not investigated the effects of extraocular muscles on the response of the eye. The purpose of the current study is to quantify the effects of the extraocular muscles using quasistatic displacement tests of the human eye in situ. A total of three post-mortem human heads were used for the matched pair tests designed to elucidate any differences in the force-deflection response of the human eye with the extraocular muscles intact and transected. Computed tomography imaging was utilized to observe the deformation of the eye within the orbit for each displacement, from 0 mm to 30 mm. Slight differences in the force-deflection response are observed; however, it is not clear how these differences will influence impact response at a dynamic rate. It was also observed that under quasistatic displacements that the eye is able to translate out of the way of the impactor assembly, even under large deflections, and without globe rupture. Additional dynamic tests are recommended to determine the effects of the extraocular muscles on eye impact response.