The refractive index of the lens is an important parameter for choosing a bai lens，
At present, the mainstream lenses on the market have refractive indices: 1.56, 1.60, 1.67, 1.71, 1.74, etc.
The refractive index of the lens. The 1.49, 1.56, 1.60, 1.67, 1.71, 1.74 on the lens refer to the refractive index of the lens.
For myopia glasses, under the same other parameters, the higher the refractive index of the lens, the edge of the lens The lower the thickness。
Under the same premise, the higher the refractive index of the lens, the thinner and lighter the lens.
However, the refractive index of the lens is not as high as possible. Generally, the higher the refractive index of the lens, the lower the Abbe number and the more obvious the dispersion. With the upgrading of lens material technology, this rule is gradually being broken.
For example, 1.71 refractive index lenses have refractive indexes higher than 1.56 and 1.67, but Abbe number is higher than 1.67 refractive index lenses and most 1.56 refractive index lenses.
