When selecting the lens, there will be 1.56, 1.61, 1.67, 1.74 and other values to choose, this value refers to the refractive index of the lens.
The higher the refractive index of the lens, the thinner the lens is and the harder the lens is. Of course, the higher the refractive index, the better the quality, and the more expensive the lens. If you want to match very thin lenses, not only with the refractive index, but also with the frame size and pupil distance.
So the point is, how do you choose the refractive index of the lens?
Many people with glasses are only the thickness of the lens, the thinner the better, will directly choose the lens with high refractive index. But in fact, the refractive index is not the higher the better, is according to the individual's own glasses to choose the right.
Why isn't the higher the refractive index the better?
First, everything is a suitable, not the more expensive the higher is the better.
Second, the higher the refractive index, the lower the Abbe number. The higher the Abbe number is, the clearer the image is. The lower the Abbe number is, the clearer the image is.
Therefore, it is generally recommended to choose the appropriate refractive index according to their own degrees.
In general.
Advice:
0°-400° myopia or < 200°-400° hyperopia: 1.56;
400°-600° myopia or 400°-600° hyperopia: choose 1.61;
600°-800° myopia: 1.67;
Above 800° choose glass lens or 1.74 resin lens.
Hope everyone healthy with eyes, more care for the soul of the window! !! See you next week
Post time: Aug-12-2022