All of the following factors can impact lens thickness except which?

• A. Bridge design
• B. Lens material
• C. Prescription power
• D. Frame size

Answer: (A)

Lens thickness is determined by the lens material, the prescription power, and the frame size. The material matters because different materials have different refractive indices; higher-index lenses bend light more efficiently, allowing for thinner lenses at the same prescription. The prescription power influences thickness because stronger powers require more material to achieve the necessary curvature, with plus lenses tending to be thicker in the center and minus lenses thicker at the edges. Frame size affects thickness since larger frames need larger lenses, which increases the overall amount of material and can raise edge thickness for minus prescriptions or center thickness for plus prescriptions. The bridge design sits on the nose and does not change the lens’ curvature or the amount of material needed, so it does not affect lens thickness.