Comparison and description of lenses' refractive index

Refractive index of lenses

Generally speaking, the thickness is inversely proportional to the index of refractive. That is, higher index of refractive represents a thinner lens. The refractive index of resin lenses that we currently use is mostly 1.50/1.56/1.6/1.67/1.74, within 1.74 is the thinnest mainstream lens (resin lens with refractive index 1.76 exists in the current market as well, but its expensive price makes it unpopular). The refractive index of PC lenses is 1.59. The figure below is the information regarding resin lenses.

Nevertheless, please note that the refractive index is not the only factor influencing the thickness of lens. These factors also include the size of frame, the pupillary distance, diopters, the axis of astigmatism, spherical and aspheric lenses, etc. Also, a higher refractive index represents a lower Abbe number (which causes chromatic aberration and worse comfort). Therefore, customers with mild nearsightedness are not recommended to wear lenses with high refractive index.

Abbe Number

In optics and lens design, the Abbe number, also known as the V-number or constringency of a transparent material, is a measure of the material's dispersion (variation of refractive index versus wavelength), with high values of V indicating low dispersion, et vice versa. Therefore, when the Abbe number is too low, the dispersion occurs on the rim of lenses.