Patterned corneal collagen crosslinking for astigmatism: computational modeling study.
OBJECTIVE
To test the hypothesis that spatially selective corneal stromal stiffening can alter corneal astigmatism and assess the effects of treatment orientation, pattern, and material model complexity in computational models using patient-specific geometries.


METHODS
Cornea and Refractive Surgery Service, Academic Eye Institute, Cleveland, Ohio, USA.


METHODS
Computational modeling study.


METHODS
Three-dimensional corneal geometries from 10 patients with corneal astigmatism were exported from a clinical tomography system (Pentacam). Corneoscleral finite element models of each eye were generated. Four candidate treatment patterns were simulated, and the effects of treatment orientation and magnitude of stiffening on anterior curvature and aberrations were studied. The effect of material model complexity on simulated outcomes was also assessed.


RESULTS
Pretreatment anterior corneal astigmatism ranged from 1.22 to 3.92 diopters (D) in a series that included regular and irregular astigmatic patterns. All simulated treatment patterns oriented on the flat axis resulted in mean reductions in corneal astigmatism and depended on the pattern geometry. The linear bow-tie pattern produced a greater mean reduction in astigmatism (1.08 D ± 0.13 [SD]; range 0.74 to 1.23 D) than other patterns tested under an assumed 2-times increase in corneal stiffness, and it had a nonlinear relationship to the degree of stiffening. The mean astigmatic effect did not change significantly with a fiber- or depth-dependent model, but it did affect the coupling ratio.


CONCLUSIONS
In silico simulations based on patient-specific geometries suggest that clinically significant reductions in astigmatism are possible with patterned collagen crosslinking. Effect magnitude was dependent on patient-specific geometry, effective stiffening pattern, and treatment orientation.


BACKGROUND
Proprietary or commercial disclosures are listed after the references.
From Cole Eye Institute (Seven, Sinha Roy, Dupps), Ocular Biomechanics and Imaging Laboratory, and the Department of Biomedical Engineering (Seven, Dupps), Lerner Research Institute, Cleveland Clinic, and the Department of Chemical and Biomedical Engineering (Seven), Cleveland State University, Cleveland, Ohio, USA; Narayana Netralaya (Sinha Roy), Bangalore, India.
Ibrahim
I
Seven
From Cole Eye Institute (Seven, Sinha Roy, Dupps), Ocular Biomechanics and Imaging Laboratory, and the Department of Biomedical Engineering (Seven, Dupps), Lerner Research Institute, Cleveland Clinic, and the Department of Chemical and Biomedical Engineering (Seven), Cleveland State University, Cleveland, Ohio, USA; Narayana Netralaya (Sinha Roy), Bangalore, India.
Abhijit
A
Sinha Roy
From Cole Eye Institute (Seven, Sinha Roy, Dupps), Ocular Biomechanics and Imaging Laboratory, and the Department of Biomedical Engineering (Seven, Dupps), Lerner Research Institute, Cleveland Clinic, and the Department of Chemical and Biomedical Engineering (Seven), Cleveland State University, Cleveland, Ohio, USA; Narayana Netralaya (Sinha Roy), Bangalore, India. Electronic address: bjdupps@sbcglobal.net.
William J
WJ
Dupps
D001251:Astigmatism / Q000188:drug therapy* / Q000378:metabolism / Q000503:physiopathology; D001696:Biomechanical Phenomena; D003094:Collagen / Q000378:metabolism*; D003198:Computer Simulation; D003319:Corneal Stroma / Q000378:metabolism* / Q000503:physiopathology; D019781:Corneal Topography; D003432:Cross-Linking Reagents / Q000627:therapeutic use*; D004548:Elasticity / Q000502:physiology; D020342:Finite Element Analysis; D006801:Humans; D017319:Photosensitizing Agents / Q000627:therapeutic use*; D012256:Riboflavin / Q000627:therapeutic use; D014466:Ultraviolet Rays
D003432:Cross-Linking Reagents; D017319:Photosensitizing Agents; D003094:Collagen; D012256:Riboflavin