What is refractive index? It is the ratio of the propagation speed of light in vacuum to the propagation speed of light in the discountglasses lens material, reflecting the refractive ability of the lens to light rays.

What is the relationship between refractive index, lens thickness, and weight? Under the same conditions, the higher the refractive index of the lens, the thinner and lighter the lens, and the higher the price.

Is a higher refractive index better? No. Different discountglasses degrees have suitable refractive ranges. If your degree is relatively low, there is no need to choose lenses with high refractive index.

The values measured by the computer optometry instrument can only be used as a reference and auxiliary for optometry due to various factors such as different machine debugging. Unless it is clearly explained to you or the degree is specified, or this note cannot be used for glasses matching.

You can see the letters S, C, and A on it. S represents the spherical lens, which is commonly referred to as myopia, C represents the cylindrical lens, commonly known as astigmatism, and A is the axial position, which is commonly referred to as the axial position. It is understood as the direction and angle of astigmatism.

The astigmatism axis of a lens is not fixed and marked, and only after the lens is processed and installed on the frame, will there be a fixed axis. It's not that if you have an astigmatism axis of 180, you should use the lens with an astigmatism axis of 180 to process it.

The thick part of the lens is in the up and down direction. The size of the eyeglass frame in the vertical direction is generally smaller, and the thickness of the lens worn out is still thinner than that in the horizontal direction.