The thickness of the cornea at any given point is measured as the normal distance between its anterior and posterior surfaces in the model. The mesh is morphed to match the geometry of the patient’s eye, and boundary conditions are applied to the clamped border of the sclera. ANSYS Mechanical uses between 60,000 and 80,000 hexagonal mesh elements, organized in five layers, to produce a 3D model of the cornea and part of the sclera (the white of the eye). Meanwhile, a script starts ANSYS Mechanical, which works unseen in the background, using the camera image as the geometry for its finite element analysis (FEA) simulations. The patient simply looks into a Pentacam camera and the doctor sees a standard image of the cornea’s front (anterior) and back (posterior) surfaces on the screen.
#ANSYS HELP SOFTWARE#
Optimeyes is a physician-friendly software product with a user interface that looks like other diagnostic software that ophthalmologists use routinely. This shows the Optimeyes software’s user interface.
#ANSYS HELP HOW TO#
The amount of deviation is critical in determining where and how to make incisions in the cornea to optimize the surgical outcome. The combination of this internal pressure with the biomechanical stiffness of the eye tissue determines the unique shape, or how much an eye deviates from the average. This fluid is formed in the ciliary process behind the iris, and it then flows through the pupil and fills the space between the iris and the cornea. Intra-ocular pressure is caused by the amount of a clear fluid called the aqueous humor in the eye. To model corneal biomechanics realistically, ISS implemented these distinct material properties in an inhomogeneous, nonlinear and anisotropic user-material Fortran function (usermat) in ANSYS Mechanical. Because our eyes encounter more UV light with time, our corneas-as any other soft biological tissue-become stiffer as we age. Ultraviolet light emitted by the sun causes crosslinks to form between the collagen fibers, adding shear stiffness to the cornea. The cornea is comprised of collagen fibers in various orientations in a matrix of polysaccharides and cells called keratocytes. The shape of the cornea is determined to a large extent by its stiffness and the internal pressure of the eye, also known as intra-ocular pressure. The question is, what is the average eye? The details of where and how to make the laser incisions-the location, length, depth and angle of the cuts-are based largely on the doctor’s experience, statistical information (so-called nomograms) and the properties of the average eye. The cornea is the transparent outermost layer of the front section of the eye, so virtually all eye surgeries, including the well-known LASIK procedure, involve cutting into the cornea to some degree. Using knowledge of the structure and material properties of the various parts of the eye, especially the cornea, ISS teamed up with ANSYS to create Optimeyes-a clinical tool for ophthalmologists that runs ANSYS Mechanical in the background to produce patient-specific surgical strategies to improve results. While this may seem like a reasonable outcome, the scientists and engineers at Integrated Scientific Services AG (ISS) knew they could do better. Still, about 30% of patients have to wear some form of corrective lens after the surgery.
In most cases, the surgery restores vision to the point that the patient has no need for glasses or contact lenses for vision correction.
The good news is that femtosecond laser surgery to remove the defective lens and replace it with an artificial intra-ocular lens is increasingly viable. ANSYS Mechanical is being used by scientists and engineers at ISS to develop the Optimeyes tool used to produce patient-specific surgical strategies to improve results.
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