Within the 2nd reporting period, the partners have finished technical development of an OCT-based 3-D multimeridian air-puff swept source OCT system (hardware and software) (objective a) which is currently being used in clinic studies. The system allows un-obstructed view of corneal deformation in multiple meridians, automatic release of trigger and capture and is patient and operator friendly. Additional strategies to increase the data acquisition throughput include polarization based, depth-enconding and spatial multiplexing, which were tested to benchmark potential ways to reduce the footprint of the system towards a compact device. Besides corneal deformation imaging, the system also allows capture of 3-dimensional OCT-based corneal topography, therefore combining in one single instrument tomographic and biomechanical measurements in a dense collection of points. An European patent office has been filed to protect this technology.
In addition to corneal macro-deformation, the ssOCT (in phase sensitive mode) has been coupled with an acoustic stimulation (speaker) module system that produces modulated micro-deformations in the cornea, envisioned as a more suitable for screening and miniaturization, folliwing predictive simulations of its prospective performance of an acoustic-stimulation system. Pre-compensation methods of the sound excitation wave and signal processing algorithms have been developed to obtain resonance frequencies, and deformation amplitudes as corneal biomarkers. An European patent office has been filed to protect this technology.
The numerical eye models developed in the 1st period have been used in the 2nd period to predict performance of different technical specifications of the imaging techniques (both macro-deformation and micro-modulated pressure), to simulate corneal response in porcine and human eyes under different pressures, to model corneal biomarkers for disease, and to retrieve corneal mechanical properties from inverse modelling. The developed software and numerical simulation studies have allowed deploying methods for: 1) estimation of IOP from corneal deformation under different recitations; 2) Methods for identification of a healthy cornea from a keratoconic cornea; 3) Automatic identification of of cone location in keratoconus; 4) Corneal material stiffness estimation.
The imaging modalities of objective a) are developed into large footprint devices. Market research suggests that there is market potential for a high-end device that combines multimeridian corneal deformation and corneal topography leading to reliable corneal material property reconstruction and predictive surgical planning, as well as for a low-cost device to be successful for disease screening and IOP measurement, we took various steps towards reduction of cost of final designs. In order to minimize risks, two strategies are ongoing. The first one (medium cost, medium size) device entails downsizing of the macro-deformation device with dedicated developments: 1) custom swept laser; 2) foot-print reduction; 3) optomechanical module 9-spot illumination module; 4) custom driving electronics; 5) low-cost digitizers. The second one (low cost, low size) device uses acoustic stimulation and replaces the OCT engine by a multiplexed high-coherence interferometry technique.
During this period, efforts have concentrated in the development of the imaging technologies, biomarkers, corneal material property reconstructions, validations and collection of the first clinical data. Clinical and model data will serve as inputs for testing custom surgical planning software. Ongoing clinical studies have included patients with normal corneas, keratoconus and forme fruste keratoconus. Preparation for clinical studies on patients B&A LASIK surgery, keratoconic patients B&A ICRS and glaucoma and keratoconic patients B&A cross-linking are ongoing.
