Refractive spherical lens S refers to the number of degrees of spherical lenses at the time of optometry. There are a number of checks that are performed during an optometry; S represents the number of diopters of the spherical lens, i.e. myopia or hyperopia, and C represents the number of diopters of the cylindrical lens, i.e. astigmatism. If S is positive, it means hyperopia, and if S is negative, it means myopia. Myopia and hyperopia are both types of refractive errors, which refer to light entering the eye and passing through the refractive medium to be imaged behind or before the retina. If the S-value detected is large, then the patient can be corrected by wearing frames, wearing corneal contact lenses or surgical correction. It is recommended that patients with refractive errors seek prompt medical attention to evaluate their condition and follow the doctor’s instructions.