The refractive index of an eyeglass online lens depends on the material used. When the center thickness is the same, lenses of the same degree and material have thinner edges than lenses with lower refractive indices.

When the eyeglasses online brands are the same, we can determine the price of the lens based on the refractive index. The higher the refractive index, the higher the price.

When the brand is different, the transparency coefficient, Abbe number, wear resistance coefficient, hardness, anti-fouling ability, and so on will all be different. The quality of the individual materials used to manufacture the lenses, the quality of the lens grinding tools, and the quality of the hardening liquid, coating, and process will also be different.

Lenses are not necessarily better with a higher refractive index. On the contrary, visually speaking, a lower refractive index may not necessarily be better. Of course, the premise is that the thickness and weight are acceptable, and the lower the better. Otherwise, first consider the issues of aesthetics and weight, and choose lenses with high refractive index.

The discount prescription glasses lens cannot be ground down from a larger size and then fitted onto a smaller frame, as it is difficult for the optical center to fully fit and there may be errors in pupil distance and height.

A lens with a convex or concave shape cut from a sphere is called a spherical lens. Due to the inevitable occurrence of aberrations (especially astigmatic aberration, and image bending aberration) in spherical lenses, a lens that corrects the shortcomings of spherical lenses has emerged - non-spherical (single-sided non-spherical).

Nonspherical lenses refer to rotating surfaces (such as parabolas) with the same non-circular cross-section on all meridians. Its biggest advantage is that there is no distortion of objects in the edge field of view, and the edges of the lens are thinner than ordinary spherical lenses.