Characterisation and Modelling of an Artificial Lens Capsule Mimicking Accommodation of Human Eyes

Abstract

A synthetic material of silicone rubber was used to construct an artificial lens capsule (ALC) in order to replicate the biomechanical behaviour of human lens capsule. The silicone rubber was characterised by monotonic and cyclic mechanical tests to reveal its hyper-elastic behaviour under uniaxial tension and simple shear as well as the rate independence. A hyper-elastic constitutive model was calibrated by the testing data and incorporated into finite element analysis (FEA). An experimental setup to simulate eye focusing (accommodation) of ALC was performed to validate the FEA model by evaluating the shape change and reaction force. The characterisation and modelling approach provided an insight into the intrinsic behaviour of materials, addressing the inflating pressure and effective stretch of ALC under the focusing process. The proposed methodology offers a virtual testing environment mimicking human capsules for the variability of dimension and stiffness, which will facilitate the verification of new ophthalmic prototype such as accommodating intraocular lenses (AIOLs).

2022 Glenn A. Fry Award lecture: Enhancing clinical assessment for improved ophthalmic management

“…The dynamics of accommodation can also be measured dynamically, and we were able to adapt commercial autorefractors 23,34–39 and, subsequently, our open-field aberrometer 27 for this purpose; with these techniques, we were able to show ciliary muscle–driven “accommodative” restoration in early accommodating intraocular lenses designs, although this was of low magnitude and was maintained only for a limited time because of fibrosis after cataract surgery, 40–42 with some lenses extending the range of clear focus mainly through aberration changes 43 . Ex vivo , these novel accommodating intraocular lens prototypes can be tested and refined through attaching them to mechanical lens stretchers, 44–46 with us recently developing a synthetic lens capsule they can be “implanted” in 47,48 …”

“…43 Ex vivo, these novel accommodating intraocular lens prototypes can be tested and refined through attaching them to mechanical lens stretchers, [44][45][46] with us recently developing a synthetic lens capsule they can be "implanted" in. 47,48 High-contrast, static visual acuity is an important safety metric 49 but is not a good predictor of functional vision. 50 Most near tasks involve an element of reading, 51 which is perceived as being critical to communication and commerce in modern societies.…”