title: Numerical model of optical coherence tomographic vibrography imaging to estimate corneal biomechanical properties.
abstract: Most techniques measuring corneal biomechanics in vivo are biased by side factors. We demonstrate the ability of optical coherence tomographic (OCT) vibrography to determine corneal material parameters, while reducing current prevalent restrictions of other techniques (such as intraocular pressure (IOP) and thickness dependency). Modal analysis was performed in a finite-element (FE) model to study the oscillation response in isolated thin corneal flaps/eye globes and to analyse the dependency of the frequency response function on: corneal elasticity, viscoelasticity, geometry (thickness and curvature), IOP and density. The model was verified experimentally in flaps from three bovine corneas and in two enucleated porcine eyes using sound excitation (100-110 dB) together with a phase-sensitive OCT to measure the frequency response function (range 50-510 Hz). Simulations showed that corneal vibration in flaps is sensitive to both, geometrical and biomechanical parameters, whereas in whole globes it is primarily sensitive to corneal biomechanical parameters only. Calculations based on the natural frequency shift revealed that flaps of the posterior cornea were 0.8 times less stiff than flaps from the anterior cornea and cross-linked corneas were 1.6 times stiffer than virgin corneas. Sensitivity analysis showed that natural vibration frequencies of whole globes were nearly independent from corneal thickness and IOP within the physiological range. OCT vibrography is a promising non-invasive technique to measure corneal elasticity without biases from corneal thickness and IOP.
authors.affiliation: Instituto de Óptica, Consejo Superior de Investigaciónes Cientificas, Madrid, Spain kling.sabine@gmail.com.
authors.forename: Sabine
authors.initials: S
authors.lastname: Kling
authors.affiliation: Wellman Center for Photomedicine and Harvard Medical School, Massachusetts General Hospital, Boston, MA, USA.
authors.forename: Imran B
authors.initials: IB
authors.lastname: Akca
authors.affiliation: Wellman Center for Photomedicine and Harvard Medical School, Massachusetts General Hospital, Boston, MA, USA.
authors.forename: Ernest W
authors.initials: EW
authors.lastname: Chang
authors.affiliation: Wellman Center for Photomedicine and Harvard Medical School, Massachusetts General Hospital, Boston, MA, USA.
authors.forename: Giuliano
authors.initials: G
authors.lastname: Scarcelli
authors.affiliation: Instituto de Óptica, Consejo Superior de Investigaciónes Cientificas, Madrid, Spain.
authors.forename: Nandor
authors.initials: N
authors.lastname: Bekesi
authors.affiliation: Wellman Center for Photomedicine and Harvard Medical School, Massachusetts General Hospital, Boston, MA, USA.
authors.forename: Seok-Hyun
authors.initials: SH
authors.lastname: Yun
authors.affiliation: Instituto de Óptica, Consejo Superior de Investigaciónes Cientificas, Madrid, Spain susana@io.cfmac.csic.es.
authors.forename: Susana
authors.initials: S
authors.lastname: Marcos
mesh_terms: D000818:Animals; D002417:Cattle; D003315:Cornea; D004548:Elasticity; D054459:Elasticity Imaging Techniques / Q000379:methods*; D008954:Models, Biological; D013552:Swine; D041623:Tomography, Optical Coherence / Q000379:methods*
keywords: corneal biomechanical properties; corneal natural frequencies; non-contact; vibrography