Determination of Corneal Nonlinear Viscoelastic Biomechanical Properties using Corvis ST Glaucoma is one of the most common eye disease in which the optic nerve gradually dies. The aim of the study is to determine the corneal biomechanical properties by modelling the corneal dynamic deformation under an air puff excitation. The corneal dynamic deformation response was modeled by using nonlinear viscoelastic model, and then benchmarked with the clinical corneal dynamic deformation profile extracted from Corneal Visualization Scheimpflug Tonometer (Corvis ST) to determine the corresponding corneal biomechanical parameters. A total of 20 normal subjects were included in this study. An optimization process was developed to determine the better combination of corneal biomechanical parameters for the normal subjects. The results showed that the model can be used to determine the corneal biomechanical properties with the corneal dynamic deformation video extracted from the Corvis ST.

Towards Realtime Estimation of a Spherical Eye Model based on a Single Fiber OCT Depth perception remains a key challenge in vitreoretinal surgery. Currently users only have the view from an overhead stereomicroscope available, but this means of visualisation is quite restrictive. Optical Coherence Tomography (OCT) has been introduced in the past and is even integrated in a number of commercial systems to provide a more detailed depth vision, even showing subsurface structures up to a few millimeters below the surface. The intraoperative use of OCT, especially in combination with robotics, is still suboptimal. At present one can get either a very slowly updating large volume scan (Cscan) or a faster but not aligned crosssectional Bscan or an even more local single point Ascan at very high update rate. In this work we propose a modelmediated approach. As the posterior eye segment can be approximated as a sphere, we propose to model the retina with this simplified sphere model, the center and radius of which can be estimated in real time. A timevarying Kalman filter is proposed here in combination with an instrumentintegrated optical fiber that provides highfrequency Ascans along the longitudinal instrument direction. The model and convergence of the model has been validated first in a simulation environment and subsequently insilico using an OCT Ascan probe mounted on a comanipulated vitreoretinal robotic system. The probe was manipulated to measure a 3D stereo lithographically printed spherical model of the posterior eye segment. The feasibility of the proposed method was demonstrated in various scenarios. For the insilico validation a 20 micrometer error and convergence speed of 2.0 seconds was found when sampling Ascans at 200Hz.