Abstract
Purpose :
The laminar region of the eye is continuously exposed to intraocular pressure (IOP) and cerebrospinal fluid pressure (CSFP) on its anterior and posterior surfaces, respectively. Body position-dependent changes in IOP and CSFP also changes translaminar pressure (TLP=IOP-CSFP), which has been hypothesized as a risk factor in glaucoma. However, there have been few studies of the resultant stresses and strains within the lamina cribrosa beams (LC) and interspersed laminar neural tissues (NT) with TLP change. This study aimed to calculate the influence of postural change (sitting vs. supine) on the resultant stresses and strains in the optic nerve head (ONH), LC, and NT, under simultaneously applied IOP and CSFP.
Methods :
Three eye-specific posterior eye finite element models were constructed, including the LC/NT microstructure, and cable elements representing anisotropic collagen fibers embedded in the peripapillary sclera and pia via a fully coupled, mesh-free, penalty-based cable-in-solid algorithm. The FE models were then subjected to three combinations of IOP and CSFP loadings consistent with postural changes; results were then interpreted in relation to the postural role in the resultant ONH, LC, and NT deformations, stresses, and strains.
Results :
Moving from sitting to supine body position caused a larger tensile, compressive, and shear stresses and strains in the ONH (Figure). IOP was the dominant (p<0.05) factor in the resultant stresses and strains in the LC and NT compared to CSFP. IOP also was the dominant factor (p<0.05) driving deformation of the anterior and posterior scleral canal openings as well as anterior and posterior laminar insertions (~ 3 times larger than CSFP) while CSFP played a pivotal role in controlling posterior laminar deformation. The cable elements representing the collagen fibers in the peripapillary sclera experienced a larger axial force in the supine compared to the sitting position, with IOP being the dominant factor compared to CSFP.
Conclusions :
Postural changes in the stresses and strains in the LC and interspersed laminar NT could improve our understanding the pathogenenic mechanisms of glaucoma, the ocular effects of idiopathic intracranial hypertension, and visual impairment in astronauts in long-duration spaceflight.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.