Thinner Lens
Lighter Weight
Strong Rx
High-Index Lenses: Thinner, Lighter Lenses for Strong Prescriptions

If your prescription is strong, high-index lenses trade lens thickness and weight for a small cost increase -- here's how to tell if you need them.

Why Strong Prescriptions Need Thicker Lenses

Standard plastic lenses bend light using their curve and thickness. The stronger your prescription -- whether nearsighted or farsighted -- the more the lens has to curve to correct your vision, which normally means a thicker, heavier lens, especially near the edges.

High-index lenses are made from a material that bends light more efficiently per unit of thickness, so they can achieve the same correction in a noticeably thinner, flatter, and lighter lens.

Index Relative Thickness Best For
1.50 (Standard) Thickest Mild prescriptions (roughly -2.00 to +2.00)
1.59 (Polycarbonate) Thinner + impact-resistant Kids, sports, moderate prescriptions
1.67 (High-Index) Thinner still Moderate to strong prescriptions
1.74 (Ultra-High-Index) Thinnest available Very strong prescriptions
Do You Need High-Index Lenses?

As a rough guideline, prescriptions beyond about -4.00 or +4.00 sphere, or high cylinder (astigmatism) values, tend to benefit noticeably from a higher index. Below that, standard or polycarbonate lenses are usually thin enough that the upgrade is more about preference than necessity.

The tradeoff: cost, not vision quality. High-index lenses correct your vision exactly the same as standard lenses of the same prescription -- the difference is purely thickness, weight, and comfort on your face.
Frequently Asked Questions
Will high-index lenses make my eyes look more normal-sized? +
Yes, to a degree. Thick standard lenses can magnify (farsighted) or minimize (nearsighted) the appearance of your eyes. Thinner high-index lenses reduce this effect noticeably.
Are high-index lenses more fragile? +
No, they are generally comparable in durability to standard lenses and often come with scratch-resistant coating by default.
What index should I choose for a -6.00 prescription? +
Most people in that range are comfortable with 1.67 high-index; very strong prescriptions (beyond -8.00 to -9.00) often move to 1.74 for a noticeably thinner result.
Does Shade Gray offer high-index lenses? +
Yes, high-index upgrades are available at checkout on new frames and through our lens replacement service for frames you already own.
More Helpful Guides
Strong prescription? Go thinner.

Upgrade to high-index lenses on any Shade Gray frame, starting at $49, or through lens replacement for glasses you already own.