Purchase this article with an account.
E.A. Kennedy, I.P. Herring, S.M. Duma; Effects of the Extraocular Muscles on the Response of the Human Eye under Dynamic Loading . Invest. Ophthalmol. Vis. Sci. 2006;47(13):5062.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
The purpose of this study is to determine the effects of the extraocular muscles on the biomechanical response of the human eye in situ for dynamic impacts.
The effects of the extraocular muscles were elucidated by matched pair testing on 5 human cadaver heads. On each specimen, the muscles were transected from one eye, while the muscles of the other eye were left intact. The impact tests were performed using a spring–powered dynamic impactor. The impactor was accelerated to a velocity of approximately 10 m/s before impacting the eye. A load cell was used to measure the loads exerted on the eye by the impactor. An accelerometer attached to the impactor assembly facilitated both inertial compensation of the impactor load and determination of impactor displacement.
Force versus displacement curves were compared between eyes with intact and transected muscles for each specimen tested. Several trends were observed from these comparisons. First, in 4 of the 5 tests, the eyes with the intact muscles developed a higher peak force than with the muscles transected, while the remaining test generated similar overall peak forces. Second, for 4 of the 5 tests, greater posterior translation was observed on the eyes with the muscles transected, while the remaining test showed marginally higher translations with the muscles intact. No differences were noted in injury outcome (globe rupture) between the eyes with muscles transected versus eyes with muscles left intact.
When all test results are compared, the force–deflection results are similar between the intact and transected muscle groups. Qualitatively, with the extraocular muscles left intact, a slightly stiffer force–deflection response and less translation occurs to the point of the peak force; however, the overall force–deflection response is not appreciably different between the two test groups. Also, no differences were noted in injury outcome suggesting that impact tests performed using a simulated orbit, even without accommodations for the extraocular muscles, can accurately replicate the in situ response of the eye. In summary, this study suggests that during impact testing of human eyes, the extraocular muscles do not have an appreciable effect on eye injury outcome, and that the overall force–deflection corridors are similar with the extraocular muscles left intact or transected.
This PDF is available to Subscribers Only