If the Rx calls for +11.00D OU spheres, the best lightweight single vision lens to use would be:

• A. Polycarbonate
• B. Hi-index
• C. Trivex
• D. CR-39

Answer: (B)

For a strong plus prescription, thinning the lens is the main goal, because higher diopters push thickness up, especially in the center. The material with the highest refractive index lets the same dioptric power be achieved with gentler curvature, meaning you can design a lens that is much thinner and lighter. That’s exactly why high-index lens materials are preferred for +11.00D – they minimize thickness and weight while preserving optical performance.

Among common options, high-index has the highest index, so it’ll produce the thinnest lens for this power. CR-39, with a lower index, would be noticeably thicker. Trivex and polycarbonate are lighter than standard CR-39, but their indices are lower than hi-index, so they won’t be as thin for such a strong plus prescription.