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What does the refractive index of glasses mean? How to choose the right refractive index lens

​&# 8203;&# 8203;&# 8203;&# 8203;&# 8203;&# 8203; Whether it is myopia or hyperopia, you need to wear glasses in order to see things clearly. When matching glasses, we all know that you need to choose the appropriate degree, but in addition to the degree, there are some glasses parameters that you need to choose carefully. The refractive index of spectacle lens is one of the important parameters, but many people don't know what the refractive index means. In this article, let's learn what the refractive index is? How to choose the right refractive index lens.

According to the material, the common spectacle lenses on the market generally include glass, resin and cosmic films (commonly known as PC films and space films). We often see the parameter of refractive index, that is, the numbers marked on the lens are 1.49, 1.56, 1.61, 1.67 and 1.74. These refer to the refractive index of the lens, and the higher the refractive index, the thinner the lens with the same luminosity.

Million super 167 aspheric discoloration gray (film change)

Resin lens is more and more favored by people. Due to its strong impact resistance and non fragile, the lens can be made thinner, and there is no problem with frameless and half frame frames. From another point of view, its advantages are also its weaknesses. It is not easy to be damaged because of its low hardness, so the wear resistance of the lens surface is not good enough and it is easy to be scratched. Although it can be hardened and coated, it still needs careful protection to maintain a long service life. Therefore, high fold 1.8 lens and 1.9 lens are also good choices for patients with high myopia. Since there are only one or two manufacturers of high folding glass lenses in China, the lenses need to be customized according to the degree of consumers.

How to select the right refractive index lens? Generally speaking, it is recommended:

1、< 300° Myopia or & lt; 200° Hyperopia: select 1.50;

2、300°- 500° Myopia or 200 DEG- 400° Hyperopia: select 1.56;

3、500°- 700° Myopia or 400 DEG- 600° Hyperopia: select 1.60;

4、700°- 1000° Select 1.67 below;

5. Glass lens or 1.74 resin sheet shall be selected for more than 1000.

What are the parameters of glasses except refractive index?

1. Dispersion and chromatic aberration: dispersion is expressed by Abbe number. The smaller the Abbe number, the worse the dispersion phenomenon. The Abbe number of the material of ophthalmic optical lens is generally between 30 and 60. Of course, for glasses, the less the dispersion phenomenon, the better, so relatively speaking, the higher the Abbe number, the better.

2. Abbe number: refractive index and Abbe number. Generally, the higher the refractive index, the lower the Abbe number. Resin lenses are the most common in the market today. Generally speaking, CR-39 lenses with refractive index of 1.50 have Abbe number of 58; The highest Abbe number of ultra-thin resin lens with refractive index of 1.6 is only 37.