What Makes High Index Lenses so Expensive?
For anyone who copes with a strong corrective vision prescription, high index lenses can be a blessing.
Why Are High Index Lenses So Expensive?
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.
The price for all these benefits is, well…the price. High index lenses have some innate drawbacks and the most obvious one is the cost. The price of high index lenses rises exponentially as the high index rating goes up, but even the lower ranges of the high index spectrum cost more than standard glass or plastic lenses…in some cases, several times as much. Why is this?
For starters, the material used to produce 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.
That may not seem like much of a variance, but when you’re talking millimeters, it can make all the difference in the world…and incorrect prescription cutting results in wasted raw material. If a high index lens is off by more than that 0.01 millimeter, the prescription will not be accurate and the lens needs to be redone. Due to the stronger, denser properties of high index material, it’s also more difficult to accurately cut, and multiple attempts might be made before getting it perfect. Wasted material (especially a material that already costs many more times the price of standard plastic or glass) results in higher costs. And those costs, naturally, are passed along to the consumer.
So when considering high index material for your next pair of lenses, be aware of the cost…and realize that price is the trade-off for superior material.