Abstract
Corneal topographers and air-puff devices aim at completely characterizing so-called corneal biomechanics, a collection of features that describes corneal behavior. The European FP7 project (PopCorn) was born with the goal of integrating both technologies. Among the novelties, computational models were included as an integral part of the clinical assessment. Automatic patient-specific (P-S) reconstruction of the cornea, alongside material prediction based on finite element simulations, optimization, and fitting were used to strive forward in a priori surgical planning. Both methodologies show good performance in retrieving the P-S geometry of the cornea (error < 1%) and the maximum deformation amplitude of a non-contact tonometry (error ~ 5%). Nevertheless, physiological and non-physiological corneas cannot be classified solely in terms of material, at least with a single experiment. Eventually, and due to the interplay of different factors (geometry, material, and pressure), results coming from air-puff devices should be handled with care.
Highlights
Corneal biomechanics is an emerging topic in ophthalmology
The geometric algorithm reconstructed the 3-D finite element (FE) model including: the patient’s topography; an average orthogonal distribution of collagen fibers; the anisotropic hyperelastic response of the corneal tissue;[5] and a free-stress algorithm that allows for recovering the natural pre-stress due to the intraocular pressure of the eye (IOP)
The dataset contained the mechanical response of the cornea to inflation experiments in humans[6] and the kinematic response of the cornea to an air puff.[7]. After filtering those by physiological response (Fig. 1, upper right), the predictors of the material model were set using four mathematical strategies: support vector regression (SVR), multiple layer perceptron (MLP), quadratic response surface (QRS), and a clustering technique based on the K nearest neighbors (K-nn)
Summary
Non-contact tonometers aim at determining the intraocular pressure of the eye (IOP) and characterizing the mechanical properties of corneal tissue by applying a short air jet (approximately 20 ms) on the cornea. Different corneal biomarkers are recorded as the cornea deforms, establishing an interesting framework to determine the mechanical properties of the corneal tissue by means of inverse optimization processes.[1] The PopCorn European project was born as an effort to combine non-contact tonometers, imaging techniques (i.e., plenoptic imaging), and computational methods to reconstruct the P-S geometry and predict the P-S material. The data from this project will be essential to reach the ultimate objective: personalized surgical simulations
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