Astigmatism derives from Greek roots, composed of the prefix of "deprivation", "a", plus the Greek root "στίγμα" which means "point". Astigmatism is a disease that affects the eye thanks to the lack of sphericity of the lens, and therefore a certain image is not punctual on the retina, and manages to manifest as a deformed spot. In other words, it is a problem that resides in the curvature of the cornea specifically, which makes it impossible for the person to have an undistorted focus of those objects that are far and close to it. This phenomenon occurs because the cornea, instead of being round, is rounded by the polesand different radii of curvature are manifested in each of the main axes. This is why when light passes through the cornea, distorted images are obtained.
Generally, what we call the cornea and the lens are curved and smooth in the same way in each of their directions, which makes it possible to focus the light rays that are directed towards the retina at the back of the eye. But if the cornea or lens are not homogeneously smooth or curved, these light rays are not refracted as they should; phenomenon that is called refractive error.
There is the type of astigmatism that occurs when the cornea has an irregular shape, which is called corneal astigmatism. But when the shape of the lens is distorted, it is called lenticular astigmatism. As a result of these types the vision either near or far of the objects becomes distorted or blurred.
The main cause of astigmatism can be hereditary, although it should be noted that in certain cases it can occur after a corneal transplant or cataract surgery. Therefore, people can be born with this disease or at least most are born with a certain degree of astigmatism that can be associated with other refractive errors such as myopia or hyperopia.
