Astigmatism


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 approach to those objects that are far and near it. This phenomenon occurs because the cornea, instead of being round, is rounded at the poles and different radii of curvature are manifested in each of the main axes. This is why when light passes through the cornea, distorted images are achieved.

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 properly; phenomenon 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 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 cornea transplant or cataract surgery. Therefore it is that people can be born with this disease or at least most are born with a certain degree of astigmatism that can be seen attached to other refractive errors such as myopia or hyperopia.