Patient-specific simulation of the intrastromal ring segment implantation in corneas with keratoconus

A Study for Parametric Morphogeometric Operators to Assist the Detection of Keratoconus

“…Several works in the finite elements field use these raw data for several purposes: to predict the response to refractive surgeries [19] or the response to the intrastromal ring segment implantation in corneas with keratoconus [18], to analyse non-surgical corneal modifications, such as applanation tonometry for intraocular pressure measurement [20], or to analyse the behaviour of corneal tissue Thus, according to the area under the curve variable calculated for the analysed parameters, it was concluded that posterior apex deviation is the parameter that provides a higher rate of discrimination between normal and keratoconus grade I corneas. Nonetheless, other relevant statistical differences between healthy and diseased eyes are present, and most of the variables studied differ between groups.…”

“…In the literature, some works that use CAD models integrate the patient-specific model concept, which provides quantitative results applicable to a specific patient [16][17][18][19][20]. This model is obtained from the so called "raw data" [21], which are generated by systems based on the projection of a slit light onto the cornea and on the principle of Scheimpflug photography [5].…”

“…Several works in the finite elements field use these raw data for several purposes: to predict the response to refractive surgeries [19] or the response to the intrastromal ring segment implantation in corneas with keratoconus [18], to analyse non-surgical corneal modifications, such as applanation tonometry for intraocular pressure measurement [20], or to analyse the behaviour of corneal tissue properties in different scenarios [16,17]. In all these cases, raw data were provided by the Pentacam (Oculus Optikgeräte GmbH, Wetzlar, Germany) [16,18], Sirius (CSO, Florence, Italy) [19,20], or Galilei (Ziemer Ophthalmic Systems AG, Port, Switzerland) [17] devices.…”

“…In all these cases, raw data were provided by the Pentacam (Oculus Optikgeräte GmbH, Wetzlar, Germany) [16,18], Sirius (CSO, Florence, Italy) [19,20], or Galilei (Ziemer Ophthalmic Systems AG, Port, Switzerland) [17] devices. However, due to extrinsic errors [5] occurring during the measurement process, the generated raw data were incomplete; thus, the authors of the mentioned works were forced to interpolate with the aim of obtaining a complete representation of the corneal surfaces and, thus, generate a 3D model of the cornea for its posterior use in the finite elements method.…”

“…An alternative to these geometric models are the zonal methods called B-Spline functions [23]. However, this technology is not extended to the ophthalmology field, and it has only been used to generate customised models of the corneal biomechanics [17,18,20]. In these cases, the raw data obtained were incomplete in the periphery and the limbus areas due to extrinsic errors during the data acquisition process, so the authors had to interpolate data in order to obtain a complete geometric model.…”