The refractive index of myopia lenses is a refractive property of optical lenses, different refractive indices represent different refractive power of lenses, simply speaking, the higher the refractive index, the thinner the lenses, so when choosing myopia lenses, you can choose a reasonable refractive index according to different degrees of myopia. It is generally considered that for mild myopia within 200 degrees, you can choose lenses with a refractive index of 1.56 or 1.50; for myopia between 200 and 400 degrees, you can choose lenses with a refractive index of 1.60; and for myopia between 400 and 800 degrees, you can choose lenses with a refractive index of 1.67. For higher degrees, more than 800 degrees, you can choose lenses with a refractive index of 1.74, which will be thinner.