Design and evaluation of a surface-changing accommodating IOL

Abstract

Purpose : To develop and evaluate design parameters of a surface-changing accommodating IOL (AIOL).

Methods : We designed an AIOL consisting of a solid lens coupled with a flexible, single-material lens. The mechanical properties of a range of hydrophilic polymers were evaluated via tensile testing. 3D finite element simulations (using ANSYS) were used to predict the AIOL performance for various combinations of geometries and materials (Young’s Modulus 0.45-1.18 MPa, refractive index (n) = 1.415-1.46). The change in anterior and posterior surface shape upon application of a 0.08 N force (equivalent to the force by the ciliary muscle) was estimated numerically, as well as the corresponding power change in an eye model (using ZEMAX). An AIOL prototype was manufactured in a 5-axis lathe and tested experimentally with a standard hydrogel material (Young’s modulus=0.65 MPa; n=1.42). Lenses were mounted in a custom 8-arm automatic mechanical stretcher. A spectral OCT system was developed for this application (840 nm; CMOS camera; acquisition rate: 50000 A-scans/s; axial resolution: ~6.9 µm). 3D scans of an AIOL in stretched and unstretched states were obtained and the surfaces were fitted by spheres in order to determine the surface change.

Results : In mechanical simulations, posterior surface of the lens was found to flatten between 1.28-7.26% and anterior surface was found to steepen between 0.51-19.83%. For off-the-shelf polymers, optical simulations predicted an equivalent change in eye power of 0.22-0.47 D. The measured changes in the manufactured AIOL geometry were flatenning of 12.3 ±0.16% for posterior surface radius and steepening of 10.56 ±3.24% for anterior surface radius, and an equatorial expansion of 0.4 mm for a 0.4 N force. These surface changes would result in a power change of 1.18 ±0.09 D.

Conclusions : Simulation and experimental methods were used to evaluate changes in surface curvature and optical performance of a new surface-changing AIOL design. The correspondence between the experimental and predicted mechanical and optical performance validated the developed platforms. While for current hydrophilic materials the evaluated design does not result in sufficient changes in power after deformation, the developed design is expected to achieve 1.5-D of effective power change with a polymer material with 0.20 MPa Young’s Modulus and n=1.46.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.