Learn more about refractive index and lens thickness

The glasses' lenses are next to the frames

Lens thickness depends on prescription strength, pupil distance (PD), frame size, and lens material.

Refractive index

Lens materials are classified according to their refractive index. This refractive index is the ratio of the speed of light passing through air to the speed of light passing through the lens material. It indicates how much the light has bent as it passes through the lens. Light is refracted or bent on the front surface of the lens and then refracted or bent again as it leaves the lens.

A denser material bends the light more, so not as much material is needed to achieve the same refraction effect as a less dense material. Thus, the lens can be made thinner and lighter (discount prescription glasses).

A graph showing the refractive index of each of our lens packs. Bronze and Silver -- 1.5| Gold -- 1.6| White Gold -- 1.67| diamonds -- 1.74

The higher the refractive index, the more light the material bends, and the thinner the lens is for a given power. Air has a refractive index of 1, while water has a refractive index of 1.33. Standard refractive index Plastic glasses lenses have a refractive index of 1.5. A medium index lens with a refractive index of 1.6, about 20% thinner than a standard lens. A high-index lens with a refractive index of 1.67 will be about 33% thinner, while a lens with a refractive index of 1.74 will be about 42% thinner.

Because lenses with a higher refractive index reflect 50% more light than standard refractive index lenses, they are always coated with multiple layers of anti-reflective coating, which will reduce the amount of reflection on the lens surface to less than 1%. These coatings can also reduce glare from headlights at night.