Contributions of shape and stiffness to accommodative loss in the ageing human lens: a finite element model assessment

Abstract

Ageing changes to the various components of the accommodative system of the eye lens contribute to the loss of focusing power. The relative contributions of each ageing component, however, are not well defined. This study investigates the contribution of geometric parameters and material properties on accommodation simulated using models based on human lenses aged 16, 35 and 48 years. Each model was tested using two different sets of material properties and a range of zonular fibre angles and compared to results from in vivo measurements. The geometries and material parameters of older and younger lens models were interchanged to investigate the role of shape and material on accommodative capacity. Results indicate that geometry has the greater role in accommodation.

The major influence of anterior and equatorial zonular fibres on the far-to-near accommodation revealed by a 3D pre-stressed model of the anterior eye

“…The geometric parameters used to develop the lens model were based on a 35-year-old human eye lens according to our previous study [29]. Geometric parameters of the ciliary body taken from Knaus et al [23], were originally from an in vivo morphological observation of the ciliary muscle using Optical Coherence Tomography (OCT) and Ultrasound Biomicroscopy (UBM) [4,5,30].…”

“…The elastic moduli assigned to the nucleus and cortex of lens were taken from measurements of Wilde et al [34], who used the non-destructive spinning lens method to determine the elasticities of the nucleus and cortex. The lens was considered as nearly incompressible [35][36][37] with a Poisson's ratio of 0.49 for the lens and 0.47 for the lens capsule and zonular fibres [29]. (Poisson's ratio is a measure of the compression in one direction when a material is being stretched in the perpendicular direction and has an upper limit of 0.5 when the material is incompressible.…”

“…(Poisson's ratio is a measure of the compression in one direction when a material is being stretched in the perpendicular direction and has an upper limit of 0.5 when the material is incompressible. A Poisson's ratio of 0.49 applies to almost incompressible behaviour and has been widely used in modelling studies of eye lenses [16][17][18]28,29].) Detailed material properties of each part are shown in Table 2.…”

Axisymmetric Finite Element Modelling of the Human Lens Complex under Cataract Surgery

“…Bag dislocation in these situations usually occurs a long time after cataract surgery, with a mean interval of 6.9-8.5 years [9][10][11]. In silico studies shall help understand the mechanics of the IOL dislocation, and study the parameters that could influence this complication, due to its increasing incidence following the increase of procedures performed to remove cataracts [12][13][14]. However, only a few computational studies on the crystalline lens are found in literature and to the authors' knowledge there are none addressing the IOL dislocation.…”

“…However, only a few computational studies on the crystalline lens are found in literature and to the authors' knowledge there are none addressing the IOL dislocation. Previously published works had different purposes, such as understanding the mechanisms of the accommodation process in healthy or presbyopic eyes [15][16][17], or computationally estimating mechanical properties of the human crystalline lens [13,18].…”