A posterior center of gravity is associated with what change in centration compared to anterior CG?

• A. Worse centration
• B. Better centration
• C. No change
• D. Variable depending on edge design

Answer: (B)

A posterior center of gravity places more of the lens weight toward the back surface, closer to the cornea and tear film. Under gravity and eyelid forces, this positioning makes the lens settle more symmetrically on the ocular surface, aligning more effectively with the corneal and pupil center. The result is better centration of the lens relative to the pupil. If the weight were toward the front, the lens would be more likely to tilt or edge-lift in relation to the eyelids, increasing decentration. So, the gravitational effect of a posterior CG tends to produce improved centration.