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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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Khalid Alghanim1
1Mechanical Engineering Department, Kuwait University, P. O. Box: 5969, Safat, 13060, Kuwait
Joseph Bentsman1
1Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, USA