Firstly, in terms of the cheapest eyeglasses material, resin lenses are a type of polymer compound that softens upon exposure to heat and has plasticity. Resin lenses are lenses formed by chemically synthesizing and processing resin as raw material.

Glass lenses are lenses made of optical glass, with slightly higher clarity than resin lenses and a higher refractive index. The highest refractive index commonly used for lens applications is 1.9. The surface hardness of glass lenses is high, making them more scratch-resistant and wear-resistant than lenses made of other materials.

The refractive index of a lens is determined by the material used for the cheapest eyeglasses lens. When the center thickness is the same, lenses of the same degree and material have a higher refractive index and thinner edges.

When the brand is the same, the difference in refractive index indicates the difference in materials used, and can also determine the price of the lens. The higher the refractive index, the higher the price, and vice versa.

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 bending aberration) in spherical lenses, there have been lenses that correct the shortcomings of spherical lenses, namely non-spherical (usually referring to single-sided non-spherical lenses).

Non-spherical lens refers to a rotating surface (such as a parabola) 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. So, the price will be relatively higher.

In addition, double-sided non-spherical lenses have also appeared on the eyeglass mart, which provides clearer visibility and better imaging effects when worn.