There is a formula for converting what degree to choose for contact lenses in clinical practice, the refraction of contact lenses = refraction of frame glasses / (1 – 0.02 x refraction of frame glasses). 0.012 represents the distance between the center of the frame lens and the vertex of the cornea, which is generally negligible for myopia below 400 degrees and does not need to be converted, and is mainly used for over 400 degrees Myopic patients. Patients with astigmatism are recommended to wear lenses with a low water content of 38% to correct astigmatism better. 75 degrees of astigmatism or less can be added to half of the astigmatism value to the degree of myopia, for example, 350 degrees of myopia plus 75 degrees of astigmatism can give the patient 375-400 degrees of myopic contact lenses. Astigmatism higher than 75 degrees is recommended to be custom made, although more expensive, but the quality of vision is clear.