With the base curve constant and a smaller diameter (looser fit), the sagittal height is

• A. Smaller
• B. Larger
• C. Ideal
• D. Unchanged

Answer: (A)

Sagittal height reflects how tall the lens sits above the cornea, especially toward the edge, and it depends on the arc of the lens’ posterior surface. When the base curve stays the same, the posterior curvature is unchanged, so central clearance is constant, but the edge arc changes with diameter. A smaller diameter means the lens covers a shorter arc of the cornea (a smaller radius from center), which reduces the edge sag or lift. Since sagitta increases with how far you move from the center, reducing the diameter lowers the sagittal height. In other words, with a fixed base curve, a smaller diameter produces less edge elevation, so the sagittal height is smaller.