Biomechanics of corneal ectasia and biomechanical treatments.
Many algorithms exist for the topographic/tomographic detection of corneas at risk for post-refractive surgery ectasia. It is proposed that the reason for the difficulty in finding a universal screening tool based on corneal morphologic features is that curvature, elevation, and pachymetric changes are all secondary signs of keratoconus and post-refractive surgery ectasia and that the primary abnormality is in the biomechanical properties. It is further proposed that the biomechanical modification is focal in nature, rather than a uniform generalized weakening, and that the focal reduction in elastic modulus precipitates a cycle of biomechanical decompensation that is driven by asymmetry in the biomechanical properties. This initiates a repeating cycle of increased strain, stress redistribution, and subsequent focal steepening and thinning. Various interventions are described in terms of how this cycle of biomechanical decompensation is interrupted, such as intrastromal corneal ring segments, which redistribute the corneal stress, and collagen crosslinking, which modifies the basic structural properties.


BACKGROUND
Proprietary or commercial disclosures are listed after the references.
From the Department of Ophthalmology and Visual Science (Roberts), Department of Biomedical Engineering, The Ohio State University, Columbus, the Cole Eye Institute and Department of Biomedical Engineering (Dupps), Lerner Research Institute, Cleveland Clinic, and the Department of Biomedical Engineering (Dupps), Case Western Reserve University, Cleveland, Ohio, USA. Electronic address: roberts.8@osu.edu.
Cynthia J
CJ
Roberts
From the Department of Ophthalmology and Visual Science (Roberts), Department of Biomedical Engineering, The Ohio State University, Columbus, the Cole Eye Institute and Department of Biomedical Engineering (Dupps), Lerner Research Institute, Cleveland Clinic, and the Department of Biomedical Engineering (Dupps), Case Western Reserve University, Cleveland, Ohio, USA.
William J
WJ
Dupps
D001696:Biomechanical Phenomena / Q000502:physiology*; D003319:Corneal Stroma / Q000503:physiopathology* / Q000601:surgery; D048988:Corneal Surgery, Laser; D019781:Corneal Topography; D004108:Dilatation, Pathologic / Q000503:physiopathology; D004548:Elasticity / Q000502:physiology*; D020342:Finite Element Analysis; D006801:Humans; D007640:Keratoconus / Q000503:physiopathology* / Q000601:surgery; D019919:Prosthesis Implantation; D013314:Stress, Mechanical