Astigmatism is a type of refractive error that is related to the curvature of the cornea and lens. Astigmatism is mainly caused by genetic and acquired eye diseases. Astigmatism is divided into regular astigmatism and irregular astigmatism. Most people have regular astigmatism, which is mainly determined by genes, just as the height of the face and the height of the body are determined by genes. The refractive medium (cornea and lens) is not a standard spherical shape, and if the curvature is curved in the horizontal angle and flattened in the vertical angle, the eye is not ortho-spherical, but like a rugby ball shape. If the eye is not round enough, there will naturally be a difference in refractive effort in different directions. This type of astigmatism can be corrected by wearing frame glasses if the degree is not too large. There is also irregular astigmatism, which is secondary to inflammation, tumor, trauma, internal and external eye surgery or corneal diseases that cause changes in the shape of the cornea, such as corneal purpura, conical cornea, pterygium, lens dislocation, etc., because of pathological changes in the “refractive elements” of the cornea or lens. Astigmatism. This type of astigmatism is irregular and cannot be corrected by frames, so contact lenses, especially specially designed contact lenses, can correct these abnormal astigmatism. Astigmatism is irreversible, mainly caused by genetic and acquired eye diseases, and can be corrected in different ways by distinguishing different types of astigmatism.