Plus lenses with minus carriers in GP lenses affect edge thickness and seating how?

• A. Edges thinner; sit lower
• B. Edges thinner; sit higher
• C. Edges thicker; sit lower
• D. Edges thicker; sit higher

Answer: (D)

In GP lens design, how the edge behaves is all about thickness distribution around the optic zone. A plus power center makes the center relatively thick, and introducing a minus carrier changes the peripheral profile so the edge area becomes thicker compared with the center. That thicker edge increases the lens’ edge lift, causing the edge to ride higher on the cornea. So, plus lenses with minus carriers tend to have a thicker edge that sits higher rather than thinner edges or lower seating.