Lens index: what 1.50, 1.60 and 1.67 mean

A material property

Refractive index describes how light travels through a material. Lens power comes from the material together with the shapes of the surfaces, not from index alone. For a comparable prescription, a higher-index material can achieve the required bending with different, often flatter, curves. That can help reduce thickness. But the finished edge also depends on the frame opening, where the eye sits within it, the lens design and the minimum thickness needed for manufacture and mounting.

Refractive index describes how a material bends light. Higher-index materials can make a given lens thinner, but a higher number does not automatically mean better vision or a lighter finished pair.

Compare the actual order

Ask for thickness estimates for the same prescription and frame, along with material, coating and price. A useful comparison changes one choice at a time; it does not rank all lenses by index alone.

A worked example

Suppose two quotes offer 1.60 and 1.67 lenses. First hold the prescription and chosen frame constant. Then ask for an estimate of the finished thickness at the thickest edge, the material and coating names, and the difference in total price. An estimate of a 1 mm saving is a geometric comparison for that order, not a universal promise for everyone with the same prescription. Weight may not fall in the same proportion because materials have different densities.