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Andrew Rau, Scott Lovald, Steven Nissman, John McNulty, Jorge Ochoa, Michael Baldwinson; The Mechanics of Corneal Deformation and Rupture for Penetrating Injury in the Human Eye. Invest. Ophthalmol. Vis. Sci. 2016;57(12):2384.
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© ARVO (1962-2015); The Authors (2016-present)
A penetrating eye injury is a surgical emergency with a guarded visual prognosis. The purpose of this study was to determine the force required to rupture the cornea with a penetrating object, and to study how this force is affected by the object geometry.
Thirty-six human cadaveric eye specimens were used for the study. Spherical indenters of three different diameters (1.0, 1.5, and 2.0 mm) were pressed into the apex of the cornea at two displacement rates (1.0 mm/s and 5.0 mm/s) until rupture of the specimen occurred. Low strain stiffness (between 3-5 mm indenter displacement), high strain stiffness (between 80%-90% of the maximum failure force), indenter displacement at failure, and the force at failure were determined from the test data and used to characterize the mechanical tissue response. Multi-variable regression analysis was performed on the output parameters in order to determine associations of the input variables (indenter size, test speed, tissue postmortem time, and specimen geometry) on the mechanics of the tissue response.
Twenty-nine of the 36 specimens failed at the location where the indenter contacted the cornea, four specimens failed at the limbus, and three specimens failed in the sclera near sites of muscle attachment. The average force at failure caused by the 1.0 mm, 1.5 mm, and 2.0 mm diameter indenters increased from 30.5±5.5 N to 40.5±8.3 N to 58.2±14.5 N, respectively (p<0.002) (Table 1, Figure 1). The force at failure was also determined to be associated with the donor age (p<0.001), and globe diameter (p<0.041), but was not associated with intraocular pressure, tissue postmortem time, axial length, or indenter speed.
This study has quantified the force-displacement response of a large series of human cadaveric eyes subjected to penetrating indentation loads on the cornea. The results provide useful data for characterizing the relationship between corneal rupture and the geometry of a penetrating object.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
The outcome measures for all test groups. Note: results presented as Avg. ± St. Dev.
Force (N) vs. displacement (mm) curves for the 1.0 mm indenter tests (specimens 25-36). Specimens that failed at the contact location in the cornea are indicated with a circle at the failure point, while specimens that failed in other regions of the eye are indicated with an X at the failure point.
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