Determining in vivo elasticity and viscosity with dynamic Scheimpflug imaging analysis in keratoconic and healthy eyes

Abstract

The paper presents a novel analysis method of corneal elasticity and viscosity based on corneal visualization Scheimpflug technology (CorVis ST) for keratoconus diagnosis. Methods for air puff force measurement and corneal imaging boundary extraction were proposed. Corneal biomechanical properties, described as tangent stiffness coefficient (STSC ) and energy absorbed area (Aabsorbed ), were assessed using the curves of the applied air puff force with corneal displacement to form a loading-unloading cycle. Twenty-five patients with keratoconus and 34 healthy control subjects, matched for intraocular pressure (IOP), were enrolled in this prospective study. The results showed that the intraclass correlation coefficients (ICC) of the STSC and Aabsorbed were 0.941 and 0.878 in Healthy group; and were 0.891 and 0.809 in Keratoconus group, respectively. Both STSC and Aabsorbed of keratoconus patients were significantly different from that of controls (both probability value P< 0.001). ROC curve analysis showed that the area under curve for STSC was 0.918 and for Aabsorbed was 0.894, which reached a good level of predictive accuracy for detecting keratoconus. Our results demonstrated that this new analysis method could be used to characterize the biomechanical properties of corneas. (a) The air puff force of CorVis ST was measured by a custom-designed force detection system. (b) Corneal displacement was extracted from CorVis ST using a proposed imaging analysis. (c) With the utilization of the air puff force and corneal dynamic displacement, an analysis method was developed to introduce new corneal biomechanical parameters - STSC and Aabsorbed .

Biophotonics in China

“…Besides the above‐mentioned representative work, the research interests of China researchers are quite diverse, covering technique development through to biomedical applications. Consulting the papers published over the last three years in Journal of Biophotonics, the hot topics include photoacoustic microscopy , other technical improvement for imaging , photodynamic therapy , and human studies .…”

Dynamics Modeling of Corneal Deformation under Air Puff with Linear and Nonlinear Viscoelastic Model

“…Fig. 8 showed that in the case of k = 65 N/m and c = 0.25 Ns/m, the corneal apex deformation cannot return back to the original position within 30 ms, and is consisted with the clinical observation that Keratoconic cornea with lower elasticity and higher viscosity take more time to fully recover to the original shape (position) [34,41,43]. The magnitude of the maximum corneal deformation (ymax) in the Fig.…”

Assessment of the influence of viscoelasticity of cornea in animal ex vivo model using air‐puff optical coherence tomography and corneal hysteresis

“…Most recent clinical system (Corvis ST, Oculus Optikgeräte GmbH, Germany) uses Scheimpflug technology and measures the corneal deformation directly in a similar way as our air‐puff SS‐OCT. We showed, however, that our system provides superior image quality comparing to Scheimpflug camera‐based Corvis device . The parameter called CH measured with ORA is defined as a difference in air‐puff pressures accompanying inward and outward applanation events during stimulation, and it should not be identified as the hysteresis analyzed in this study .…”

“…The parameter called CH measured with ORA is defined as a difference in air‐puff pressures accompanying inward and outward applanation events during stimulation, and it should not be identified as the hysteresis analyzed in this study . Wang et al used high‐speed Scheimpflug imaging along with pre‐measured force wave to determine the hysteresis in keratoconus patients . However, the proposed methodology did not take into account the movement of the whole eye globe that was reported for such in vivo measurements .…”