The optic nerve head as a biomechanical structure: initial finite element modeling.

摘要: Purpose To study the relationship between intraocular pressure (IOP) and IOP-related stress (force/cross-sectional area) it generates within load-bearing connective tissues of optic nerve head. Methods Thirteen digital, three-dimensional geometries were created representing posterior scleral shell 13 idealized human eyes. Each geometry was then discretized into a finite element model consisting 900 constituent elements. In five models, canal circular (diameters 0.50, 1.50, 1.75, 2.00, 2.56 mm), with wall thickness (0.8 mm) inner radius (12.0 held constant. three elliptical (vertical-to-horizontal ratios 2:1 [2.50 x 1.25 mm], 1.5:1 [2.1 1.4 1.15:1 [1.92 1.67 mm]), same constant radius. additional size (1.92 either (three 0.5, 1.0, 1.5 or (two 13.0 14.0 varied. all each assigned single isotropic material property, (modulus elasticity, 5500 kPa) axonal 55 kPa). Maximum stresses specific regions calculated at an IOP 15 mm Hg (2000 Pa). Results Larger diameter, elongation canal, thinning sclera increased for given level IOP. For maximum ranged from 6 (posterior sclera) to 122 (laminar trabeculae). model, highest laminar trabecular region decreased progressively through insertion, peripapillary scleral, regions. Varying had little effect on canal. Conclusions Initial models show that head is substantial even low levels Although data suggest shape are principal determinants magnitude head, incorporate physiologic geometries, more refined meshwork, nonisotropic properties will be required confirm these results.