why are high index lenses expensive?

[Gap Mills]

Can anyone tell me why high index lenses are so expensive from the opticians??

[Odon]

For many reasons, such as High index lenses are essentially the diamond ring of lens materials. They offer the sharpest optical quality, the thinnest (and best-looking) profile, and, usually, the lightest weight. The material the lenses are made of is a synthetic plastic that (in general) took a fair amount of research and chemistry to create.high index plasitic always costs more than traditional plastics or polycarbonate to manufacture. High index lenses have more overhead cost in the optical lab because they are completely unforgiving when you're generating a prescription into them.

[Castleberry]

high index lenses require less physical material to form a prescription, which means they can be significantly lighter and thinner than an identical?prescription?cut of standard plastic or glass.High index lenses may allow you to choose?frames?you never before could have selected. And maybe best of all, the magnification distortions that create a bug eye or tiny eye effect can be greatly diminished.

[Monteview]

The price of high index lenses rises up exponentially as the high index rating goes up.Firstly because the material used to product high index lenses is a chemical synthetic blend.The raw material cost, just to produce sheets of the high index glass or plastic used for the lenses, is very high on a production level. Even 1.67 and 1.70, the lower ends of the high index range, cost more than double the price to produce than standard glass or plastic material. 1.74 high index plastic is about three times as expensive, and the high index glass options take another quantum leap forward in raw materials cost. A second factor affecting price is the "wasted material" factor. High index lenses have a tighter tolerance range in prescription cutting than standard plastic or glass. This translates into less leeway for error. Traditional plastic can allow a difference of plus or minus 0.1 millimeter and still fall within guidelines for a particular prescription. High index material will only allow a variance of plus or minus 0.01 millimeter.