How to choose the refractive index of myopia lenses? _Lens knowledge
As for the lens material, most people may be familiar with it. The descriptions of the lenses we have seen have refractive indexes of 1.49, 1.56, 1.61, 1.67, etc. These numbers all represent the optical refractive index of the lens. Different materials have different refractive indices. Let's take a look at the refractive index of myopia lenses. The refractive index refers to the ratio of the sine of the transmitted light angle to the light incident from the air and the sine of the incident light angle specific to the medium. The value of the refractive index is generally between 1.49 and 1.74. When the center thickness of the lens is the same, the power is the same, and the material is the same, the larger the number, the thinner the lens, that is, the higher the refractive index, the thinner the lens. Different degrees are suitable for different refractive indexes. The choice of the refractive index of the spectacle lens is also based. The following lens power and lens refractive index are only a reference, and the specific individual lens selection needs to be selected according to the actual situation. Power lens name selection lens refractive index selection within 300 degrees ordinary lens 1.560-500 degrees medium refractive index lens 1.61300-600 degrees medium refractive index aspheric lens 1.61 aspheric surface 400-800 degrees high refractive index ultra-thin 1.67500-1000 degrees high refractive index Ultra-thin 1.74 aspheric surface 1000 degrees or more, high refractive index ultra-thin aspheric lens 1.74 aspheric lens, if the myopia power is within 500 degrees, generally choose the refractive index of 1.61, this kind of lens, the lens is relatively thin, and this kind of lens There are many types in the market, and the price is relatively moderate. If the degree of myopia is above 500 degrees, considering the thickness of the lens, you can choose an aspheric lens with a refractive index of 1.67 or a lens with a higher refractive index than this. If the degree of myopia is relatively low, it is easier to choose the refractive index of the lens. Generally, ordinary lenses are better. High refractive index lenses are a bit more expensive than low refractive index lenses, and, in terms of correcting vision, low refractive index and high refractive index are the same, but the high refractive index is because the lens is thinner and the appearance is more beautiful. Individuals’ living environment and requirements for lenses are different, and the relationship between lens thickness and refractive index will also affect the choice of lenses, which need to be selected according to the specific circumstances of the individual.