What is the physical center of a spectacle lens on a frame called?

What is the physical center of a spectacle lens on a frame called?

• A. Geometric center
• B. Optical center
• C. Pupil center
• D. Bifocal center

Answer: (A)

The physical center of a spectacle lens on a frame is the geometric center. This is the point that represents the lens’s inherent, purely geometric middle—the center of the lens’s shape itself, regardless of how the lens bends light or how it sits in the frame. The optical center, on the other hand, is a separate concept: the specific point through which light passes with minimal or no prismatic deviation, which can be offset from the geometric center depending on design and alignment. The pupil center relates to the wearer’s eye pupil location, not the lens’s physical center, and the term for bifocals isn’t used to denote the lens’s center.

The physical center of a spectacle lens on a frame is the geometric center. This is the point that represents the lens’s inherent, purely geometric middle—the center of the lens’s shape itself, regardless of how the lens bends light or how it sits in the frame. The optical center, on the other hand, is a separate concept: the specific point through which light passes with minimal or no prismatic deviation, which can be offset from the geometric center depending on design and alignment. The pupil center relates to the wearer’s eye pupil location, not the lens’s physical center, and the term for bifocals isn’t used to denote the lens’s center.