Astigmatism also increases the thickness of the lens, and this is analyzed in terms of the principle of astigmatism correction. Astigmatism is caused by the unevenness of the curvature of the cornea, that is, the refractive power of the eye is different in different meridians, for example, the position of the highest refractive power shows a myopic state, this situation is called myopic astigmatism, and the part of the highest refractive power shows a hyperopic state, it is called hyperopic astigmatism. The correction of these conditions is mainly done through toric lenses, so in principle, this is also a correction of myopia or hyperopia, which will increase the thickness of some lenses, depending on the degree of astigmatism. For large astigmatism, such as over 300 degrees of astigmatism, it is generally recommended to give preference to corneal contact lenses rather than frame glasses.