With a larger diameter and a constant base curve, which statement best describes sagittal height and fit?

With a larger diameter and a constant base curve, which statement best describes sagittal height and fit?

• A. Sagittal height decreases; fit tightens.
• B. Sagittal height remains the same; fit is loose.
• C. Sagittal height increases; fit becomes looser.
• D. Sagittal height increases; fit becomes tighter.

Answer: (D)

Increasing the lens diameter while keeping the base curve fixed changes the sag of the lens. Sagittal height is the depth of the lens’s curve in the sagittal plane, and as the diameter gets larger, the lens must bend over a wider arc. That extra arc bend raises the sagittal height. With a higher sagittal height, the lens sits more tightly over the cornea and toward the sclera, limiting its movement. The central curvature stays the same, so the change is in how much the lens edge engages the peripheral area—leading to a tighter fit. So, larger diameter plus constant base curve increases sagittal height and makes the fit tighter.

Increasing the lens diameter while keeping the base curve fixed changes the sag of the lens. Sagittal height is the depth of the lens’s curve in the sagittal plane, and as the diameter gets larger, the lens must bend over a wider arc. That extra arc bend raises the sagittal height.

With a higher sagittal height, the lens sits more tightly over the cornea and toward the sclera, limiting its movement. The central curvature stays the same, so the change is in how much the lens edge engages the peripheral area—leading to a tighter fit.

So, larger diameter plus constant base curve increases sagittal height and makes the fit tighter.