Compared with an equivalent spherical lens, a plus aspheric lens with decreased center thickness tends to have what change in both lens volume and weight?

• A. Volume increases and weight increases
• B. Volume remains the same and weight remains the same
• C. Volume decreases and weight decreases
• D. Volume increases while weight decreases

Answer: (C)

The main idea is that material use governs weight. For a plus lens with the same overall power and diameter, an aspheric design can achieve the same focal effect while reducing the amount of glass in the center. Thinning the center lowers the average thickness across the lens, so the total volume of material drops. Since weight is basically proportional to volume (assuming similar material), the lens becomes lighter as well. The edges may remain thick enough for mounting and structural needs, but the central thinning drives both volume and weight down. That’s why the correct outcome is that both volume and weight decrease.