# Biomechanical Study of the Eye with Keratoconus-Type
## 1 Introduction  
The cornea is a transparent, convex structure that forms the front and outer parts of the human eye. It is located on the anterior surface of the eyeball and is an essential part of vision, as it plays several crucial roles in the visual process [1]. One of these functions is to protect the eye from factors such as dust and germs and to control the entry of light [2]. However, for the cornea to achieve its goal, it must be transparent, and it is imperative to maintain adequate curvature [2]. The morphological characterization of the cornea is key in clinical practice because it is pertinent to visualize the changes in the cornea that could affect the visual quality of patients, the evolution of the disease, the diagnosis, and subsequent treatment in certain ocular pathologies [3]. Keratoconus is an ocular pathology that occurs in the cornea of the eye, produces image distortion, and progressively reduces vision. It is a bilateral, non-inflammatory corneal ectasia that causes myopic astigmatism and decreased visual acuity [4]. This degenerative disease arises from a constant thinning of the thickness of the cornea in the central and paracentral areas, in addition to a change in the normal spherical curvature ofthe eye, thus creating a cone-shaped cornea [5]. The onset of this disease commonly occurs in only one eye, whereas the other remains normal. There have been keratoconsu cases in which patients reported decreased visual acuity, frequent lens changes, image distortion, and varying degrees of contact lens discomfort early in the disease [6]. Keratoconus is affecting more and more people around the world, especially in places with high exposure to ultraviolet rays, such as Ecuador. This pathology produces a high level of astigmatism that hinders clear vision. In addition, severe cases of this disease may require a surgical procedure of corneal transplant due to the opacity generated by corneal ectasia [5]. This condition has been the focus of several studies due to its severity in the human eye; hence, several methods have been developed to characterize this pathology. Some methods are as non-invasive as possible, avoiding the use of anesthesia or having direct contact with the eye during the integral characterization of the corneal topography [7]. Ophthalmologic examinations, such as corneal topography and optical coherence tomography (OCT), that map the surface and internal structure of the cornea are typically used for early diagnosis [8]. Early treatment, such as rigid contact lenses, can help correct vision in the early stages of the disease, while corneal transplants are an option in severe situations, as this can considerably improve the patient's vision and quality of life [8]. Pentacam(r) is capable of capturing data from the surface of the anterior cornea to the posterior capsule of the lens [9]. This camera provides sharp and bright images, improving image quality compared to other optical cameras [10]. Pentacam(r) provides data on anterior and posterior corneal topography, elevation maps, pachymetry, 3D camera analysis, intraocular pressure (IOP), and many other parameters to support the diagnosis and subsequent treatment of the disease [11]. This work proposes a three-dimensional approach to investigate the biomechanics of the eyes affected by keratocons, thus showing the creation process of geometric models for patients with ectasia in the case of keratoconsu type, keratoglobus, and a non-pathological eye. The strategy for this study was to create a realistic customized 3D model, as it provides accuracy in how certain geometric aspects of the cornea influence the biomechanics and progression of the disease. With these aspects, it was possible to build an investigation using the data of the examination of patients from an authorized database in the form of point clouds exported by Pentacam(r); Rhinoceros(r) processed these points to build the 3D models.The model was executed in ABAQUS(r), in which a finite element analysis was performed [12].