Predicting the biomechanical stability of IOLs inside the postcataract capsular bag with a finite element model

Implantation of a capsular tension ring during cataract surgery attenuates predicted remodeling of the post-surgical lens capsule along the visual axis

Introduction: Cataract surgery permanently alters the mechanical environment of the lens capsule by placing a hole in the anterior portion and implanting an intraocular lens (IOL) that has a very different geometry from the native lens. We hypothesized that implant configuration and mechanical interactions with the post-surgical lens capsule play a key role in determining long-term fibrotic remodeling. Methods: We developed the first finite element-growth and remodeling (FE-G&R) model of the post-surgical lens capsule to evaluate how implantation of an IOL with and without a capsular tension ring (CTR) impacted evolving lens capsule mechanics and associated fibrosis over time after cataract surgery. Results: Our models predicted that implantation of a CTR with the IOL into the post-surgical lens capsule reduced the mechanical perturbation, thickening, and stiffening along the visual axis in both the remnant anterior and posterior portions compared to implantation of the IOL alone. Discussion: These findings align with patient studies and suggest that implantation of a CTR with the IOL during routine cataract surgery would attenuate the incidence of visually-debilitating capsule fibrosis. Our work demonstrates that use of such modeling techniques has substantial potential to aid in the design of better surgical strategies and implants.

Influence of design parameters and capsulorhexis on intraocular lens stabilities: A 3D finite element analysis

BACKGROUND

Current treatment of cataract widely used in clinics is by removal of the opacified content from the lens capsule which is followed by insertion of an artificial intraocular lens (IOL). The IOL needs to remain stabilized in the capsular bag for the eye to achieve desired optical quality. The present study aims to investigate how different design parameters of the IOL can influence the axial and rotational stabilities of IOLs using Finite Element Analysis.

METHODS

Eight designs of IOL with variations in types of optics surface, types of haptics and haptic angulation were constructed using parameters obtained from an online IOL databank (IOLs.eu). Each IOL was subjected to compressional simulations both by two clamps and by a collapsed natural lens capsule with an anterior rhexis. Comparisons were made between the two scenarios on axial displacement, rotation, and distribution of stresses.

RESULTS

The clamps compression method set out by ISO does not always produce the same outcome as the in-the-bag analysis. The open-loop IOLs show better axial stability while the closed-loop IOLs show better rotational stability when compressed by two clamps. Simulations of IOL in the capsular bag only demonstrate better rotational stability for closed-loop designs.

CONCLUSIONS

The rotational stability of an IOL is largely dependent on its haptic design whilst the axial stability is affected by the appearance of the rhexis to the anterior capsule which has a major influence on designs with a haptic angulation.