July 2019
Volume 60, Issue 9
Open Access
ARVO Annual Meeting Abstract  |   July 2019
3D Patient-Specific Finite Element Model (FEM) of Intracorneal Ring Segment (ICRS) Implantation
Author Affiliations & Notes
  • Ibrahim Seven
    Ophthalmic Research, Cleveland Clinic, Cleveland , Ohio, United States
  • Rafael Grytz
    Ophthalmic Research, University of Alabama at Birmingham, Birmingham, Alabama, United States
  • William J Dupps
    Ophthalmic Research, Cleveland Clinic, Cleveland , Ohio, United States
  • Footnotes
    Commercial Relationships   Ibrahim Seven, OptoQuest (C); Rafael Grytz, OptoQuest (C); William Dupps, OptoQuest (P)
  • Footnotes
    Support  R01 EY023381; Ohio Third Frontier Innovation Platform Award TECH 13 - 059; Unrestricted Grant from RPB to the Dept. of Ophth almology of the Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, NIH / NEI P30 Core Grant (IP30EY025585 ), Unrestricted Grant from Research to Prevent Blindness to the Department of Ophthalmology, Cole Eye Institute (RPB1508DM ) , Sara J. Cheheyl Fund for Ocular Biomechanics Research and Pender Family Research Fund at the Cole Eye Institute
Investigative Ophthalmology & Visual Science July 2019, Vol.60, 6835. doi:
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    • Get Citation

      Ibrahim Seven, Rafael Grytz, William J Dupps; 3D Patient-Specific Finite Element Model (FEM) of Intracorneal Ring Segment (ICRS) Implantation. Invest. Ophthalmol. Vis. Sci. 2019;60(9):6835.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose : To develop a microstructural-based, 3D, patient-specific, finite element model (FEM) of intra-corneal ring segment (ICRS) implantation.

Methods :
Patient-specific tomographic data from two eyes of two patients undergoing ICRS implantation (450-um-height hexagonal with curved base (HCB) and 200-um-height triangle with flat base (TFB)) were used to build a corneo-scleral mesh, including a generic variable-thickness sclera using a custom meshing software. The collagen fiber distribution was modeled to simulate the anisotropic material response of the cornea, limbus, and sclera using the open source FEM software Calculix. Pre-existing stresses and strains were calculated prior to the ICRS implant simulation. Following the FE simulations, post-operative epithelium re-profiling (post-ER) was performed based on the degree of the local concavity and convexity of the elevation difference map (Figure 1). The post-operative change in the magnitude and location of the highest maximum principal strains (HMPS) were investigated. The simulated surgically-induced central flattening, the difference in average curvature within the central 3 mm circular region (ΔKmean: Diopters(D)), was compared to the actual tomographies.

Results :
At pre-op, the HMPS were 0.25% and 0.63% for the HCB and TFB cases, respectively. At post-op, the HMPS were 2.07% (HCB) and 1.31% (TFB). Post-op clinical ΔKmean were -1.45 D (HCB) and -0.69 D (TCB). FEM predicted ΔKmean were -3.51 D (HCB) and -3.63 D (TFB). FE simulations combined with post-ER predicted ΔKmean were -0.95 D (HCB) and -0.99 D (TFB) (Figure 2).

Conclusions :
FEM predicted the post-operative flattening of the central cornea within 0.50 D of actual change in modeled cases. ICRS implantation induces strain to the cornea around the implant region. Accounting for postoperative epithelial smoothing is important to avoid overestimation of surgically induced flattening.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.

 


Figure 1. Computational pipeline. i) translation of topography into mesh; (ii) simulating the pre-existing stress; (iii) simulating the incision and insertion of the implant; (iv) applying ER.


Figure 1. Computational pipeline. i) translation of topography into mesh; (ii) simulating the pre-existing stress; (iii) simulating the incision and insertion of the implant; (iv) applying ER.

 


Figure 2. Tangential curvature maps of the A) pre-op clinical, B) post-op clinical, C) post-op FEM, D) post-op FEM and post-ER. FEM: Finite element model, ER: Epithelium re-profiling.


Figure 2. Tangential curvature maps of the A) pre-op clinical, B) post-op clinical, C) post-op FEM, D) post-op FEM and post-ER. FEM: Finite element model, ER: Epithelium re-profiling.

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