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J. Chen, R. Augusteyn, A. Ho; Predicting the Influence of Lens Refilling Gel and Capsule Properties on Accommodation by Finite Element Analysis . Invest. Ophthalmol. Vis. Sci. 2006;47(13):5862.
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© ARVO (1962-2015); The Authors (2016-present)
Few theoretical studies have been done to analyse gel lens refilling for restoring accommodation. We modelled the performance of lens refilling by constructing an improved model using the finite element (FE) method.
A 2–D axisymmetric model of a 29 yo lens was constructed using the FE package Marc Mentat 2005. This model improved on a previous model (Chen et al, 2005) by incorporating a modified version of the zonule arrangements and ciliary body based on Stach et al (2005). The ciliary body was stretched radially from its fully accommodated position to a distance of 0.36 mm over 5 increments. Geometric nonlinear algorithm was used. Five capsule moduli (CM; 0.25×, 0.5×, 1×, 2×, 4× published mean values) and five refilling gel moduli (GM; 0.25×, 0.5×, 1×, 2×, 4× published mean values) were cross–simulated to build a 5 × 5 results matrix (total of 25 combinations). For each combination, changes in axial thickness (AT), semi–diameter (SD) and zonular tension (ZT) were calculated and 6th–order even polynomials were fitted to the anterior and posterior lens surfaces at each increment.
For a given CM, stretched AT increased and stretched SD decreased as GM increased. e.g. At 1× mean CM and increasing GM, stretched AT changed from 3.21 mm to 3.55 mm (unstretched AT = 4.13 mm) and stretched SD decreased from 4.65 mm to 4.63 mm (unstretched SD = 4.32 mm). ZT increased approximately linearly as GM increased (e.g. from 0.13 N to 0.24 N at 1× CM). For a given GM, stretched AT and SD decreased as CM increased. e.g. At 4× GM and increasing CM, AT and SD decreased from 3.61 mm to 3.52 mm and 4.64 mm to 4.59 mm respectively while ZT increased from 0.16 N to 0.47 N. These results agree with ex vivo human eye measurements (Parel et al, 2002).
FE provides a reliable prediction for the performance of lens refilling. For lens refilling, injecting a stiffer gel results in a less deformable lens, hence less accommodative amplitude.
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