The 1.56 refractive index of 1.56 lenses refers to the refractive index of the lenses, which is the ability of the lenses to converge light. 1.56 refractive index lenses are lenses with a lower refractive index and are more suitable for people with low myopia, or moderate to low myopia. In case of high myopia, or super high myopia, 1.67 or 1.71 refractive index lenses are recommended for lighter and thinner mirror wear. There are also 1.74 refractive index lenses available on the market, but the price may be higher, so myopic patients need to choose lenses with different refractive index types according to their needs.