In a plus aspheric lens with decreased center thickness, what change occurs to lens weight?

• A. Increase
• B. Decrease
• C. No change
• D. Unknown

Answer: (B)

Weight of a lens is determined by its volume, since density is assumed constant. In a plus aspheric lens, the center region is thicker and contributes significantly to the total material mass. If the center thickness is decreased, material is removed from the core, reducing the overall volume of the lens. With less material while the same edge dimensions are kept, the total weight drops. The optical power can remain governed by the surface curvatures, but thinning the center simply lowers weight without necessarily increasing edge thickness to compensate. So the weight decreases.