Which refractive index fits my visual values?
The thickness of your lenses depends upon the dioptre number. The higher your dioptre number is, the thicker your lenses will be. It means that people having higher correction values have to wear heavy lenses, which could get quite uncomfortable in the long run. This is where the refractive index plays its role as it can considerably increase or decrease your lenses’ thickness.
The refractive index represents the strength of light refraction. A higher value of refractive index means that light is refracted more strongly through your lens. This is why the eyeglass lenses with higher refractive indexes can be manufactured in a thin shape. The level of the refractive index also depends upon the material of glass used in your lenses. For plastic, the refractive index could be somewhere between 1.5 – 1.74, while for mineral glass, it can reach between 1.5 – 1.9.
Refractive index 1.5
These spherical are used to correct minor values up to ±2 diopters. If the value is greater than 2, then they are not suitable.
Index of refraction 1.6
If the diopter values are between ±2 to ±4, then lenses with refractive index 1.6 are used. They are much thinner and lighter as compared to the standard glasses.
Refractive index 1.67
If the diopter values are between ±4 to ±6, then lenses with refractive index 1.67 are used. These lenses are around 60% lighter as compared to standard lenses of 1.5 refractive index.
Refractive index 1.74
These are super thin lenses and are almost 60 times lighter than standard lenses. They are usually used if the dioptre value is six or above.