A finite element model investigating the cyclic strains in the lamina cribrosa and their potential role in glaucoma

Abstract

Purpose: To present the cyclic strains developed in the lamina cribrosa due to the cardiac cycle-driven fluctuations in the pressure conditions around the optic nerve head. Design: Finite element analysis on 3-D models of the human eye. Methods: Varying intraocular pressure and cerebrospinal fluid pressure over a cardiac cycle were provided as boundary conditions in the finite element models. The cyclic strains generated in the lamina cribrosa were compared at differentmean intraocular pressures representing normal and pathological conditions. Results: The peak maximum principal strains varied from 0.7% to 1.4% across all cases of normal and elevated intraocular pressure, and occurred along the periphery of the lamina cribrosa. The amplitude of the cyclic strains in the lamina cribrosa increased by 3.5% from the normal case to the pathological cases. The amplitudes did not change significantly for the pathological cases with mean intraocular pressures of 21.6 mmHg, 26.6 mmHg, and 31.6 mmHg. Conclusion and future perspective: The effect of short-term pressure changes on the tissues of the optic nerve head has not been studied extensively. In vitro and ex vivo experiments can be designed based on the results of computational studies to observe the eff ect of cyclic strains on mechanosensitive cells in the optic nerve head. Furthermore, the repetitive impact of cyclic strains in the lamina cribrosa over numerous cardiac cycles gives rise to the possibility of mechanical fatigue contributing to the structural damage around the optic nerve head. A cumulative damage model can be developed based on the results of this study.