Which of the following four measurements should be considered for soft lens selection?

Which of the following four measurements should be considered for soft lens selection?

• A. Power (D), Diameter (OAD or DIA), Sagittal Height (CL-SAG)
• B. Power (D), Radius (mm), Base Curve (BC), Sagittal Height (CL-SAG)
• C. Power (D), Diameter (OAD or DIA), Base Curve (BC), Refractive Index
• D. Power (D), Diameter (OAD or DIA), Base Curve (BC), Sagittal Height (CL-SAG)

Answer: (D)

Soft lens selection hinges on matching both the vision correction and the eye’s shape to a lens that sits comfortably and rides well on the eye. The four measurements you use talk directly to that fit: the power (how much correction is needed), the overall diameter (how wide the lens covers the cornea, affecting centration and movement), the base curve (the curvature of the lens that sits on the eye to align with the corneal surface), and the sagittal height (the lens’s vertical dimension that influences how the lens vaults over the cornea and interacts with the eyelids). Together, these determine whether the lens sits properly, moves appropriately with blinking, and stays centered while delivering the correct optics. Radius isn’t a separate fit parameter for soft lenses in routine practice because base curve already encodes the curvature the lens uses on the eye, and diameter handles how wide the lens sits across the cornea. Refractive index is a material property affecting optics in manufacturing, not a clinical fitting parameter you adjust for individual wearers. So the combination that directly guides both the optical correction and the fit for a soft lens is power, diameter, base curve, and sagittal height.

Soft lens selection hinges on matching both the vision correction and the eye’s shape to a lens that sits comfortably and rides well on the eye. The four measurements you use talk directly to that fit: the power (how much correction is needed), the overall diameter (how wide the lens covers the cornea, affecting centration and movement), the base curve (the curvature of the lens that sits on the eye to align with the corneal surface), and the sagittal height (the lens’s vertical dimension that influences how the lens vaults over the cornea and interacts with the eyelids). Together, these determine whether the lens sits properly, moves appropriately with blinking, and stays centered while delivering the correct optics.

Radius isn’t a separate fit parameter for soft lenses in routine practice because base curve already encodes the curvature the lens uses on the eye, and diameter handles how wide the lens sits across the cornea. Refractive index is a material property affecting optics in manufacturing, not a clinical fitting parameter you adjust for individual wearers. So the combination that directly guides both the optical correction and the fit for a soft lens is power, diameter, base curve, and sagittal height.