Which statement best describes the relationship between base curve steepness and sag?

Which statement best describes the relationship between base curve steepness and sag?

• A. Sag increases with steeper base curve
• B. Sag decreases with steeper base curve
• C. Sag unchanged by base curve
• D. Sag depends only on OAD

Answer: (A)

Sag measures how much the back surface of the lens sits away from the cornea across the lens diameter. When you steepen the base curve, you reduce the radius of curvature, making the posterior surface bend more sharply. That sharper bend increases the vertical depth between the center and the edge of the lens’ posterior surface, so sag goes up. In other words, a steeper base curve creates greater sag. The other ideas aren’t correct because sag is driven mainly by the curvature of the lens back surface, not kept the same, reduced with steepening, or determined only by the overall diameter.

Sag measures how much the back surface of the lens sits away from the cornea across the lens diameter. When you steepen the base curve, you reduce the radius of curvature, making the posterior surface bend more sharply. That sharper bend increases the vertical depth between the center and the edge of the lens’ posterior surface, so sag goes up. In other words, a steeper base curve creates greater sag. The other ideas aren’t correct because sag is driven mainly by the curvature of the lens back surface, not kept the same, reduced with steepening, or determined only by the overall diameter.