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Patient-Specific Optimization of Customized Corneal Cross-Linking Using Regional Stress–Strain Index Deficit Maps: A Computational Biomechanics Study

John Michael Owen1
1Emeritus Professor of Aerospace Engineering / Department of Mechanical Engineering, University of Bath

Abstract

The regional SSI mapping enabled the spatial material description of keratoconus-induced softening in place of its previous representation as a global biomechanical variable. In this context, the present investigation poses the question: could the spatial nature of regional SSI deficits be exploited to design customized keratoconus CXL? For that purpose, the study adopted a computational method to translate a presurgical SSI deficit map of keratoconus into a stiffness-deficit map, represented as Gaussian sector-based fields of anisotropic treatment, and evaluated by simulation under optical, biomechanical, and geometrical constraints. A group of 48 hypothetical eyes was modeled using combinations of four cone radii, three cone decentration values, two orientations, and two keratoconus severities. The proposed map-optimized CXL (MO-CXL) method was compared to centered circle-based CXL (CCXL), decentered circle-based CXL (DCXL), and symmetrical bow-tie CXL (BCXL). Map optimization led to designs with minimal residual cone stiffness deficit (9.7 ± 3.7%), peak cone strain (5.9 ± 1.3%), root-mean-square curvature disturbance (0.86 ± 0.31 D), and total treated area (20.7 ± 2.8 mm2) while fully maintaining safety requirements. With regard to the baseline CCXL strategy, MO-CXL reduced the deficit, strain, curvature, and treated area by 54.7%, 32.2%, 53.3%, and 58.8%, respectively. The results thus answered positively the research question raised at the outset: yes, regional SSI maps can be effectively utilized as design targets in computationally tailored CXL plans.

Keywords: keratoconus; corneal biomechanics; corneal cross-linking; stress–strain index; finite element analysis; patient-specific treatment; optimization
Citation
John Michael Owen. Patient-Specific Optimization of Customized Corneal Cross-Linking Using Regional Stress–Strain Index Deficit Maps: A Computational Biomechanics Study[J], TK Techforum Journal (ThyssenKrupp Techforum), Volume 2021 (3). 103-116.

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Joseph Bentsman1
1Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, USA
S. Sheyko1, O. Hrechanyi1, T. Vasilchenko1, A. Hrechana2
1Department of Metallurgical Equipment, Zaporizhzhia National University, Zaporizhzhia, Ukraine
2Scientific Laboratory of the Latest Technologies, Educational and Scientific Production Center “Metalspetsproekt,” Zaporizhzhia National University, Zaporizhzhia, Ukraine