A lens with two different curves on the back and one spherical front curve is known as a:

A lens with two different curves on the back and one spherical front curve is known as a:

• A. Toric Base Curve Lens
• B. Spherical Base Lens
• C. Multicurve Back Lens
• D. Flat Back Curve Lens

Answer: (A)

Two different curvatures on the back surface mean the back is toric, providing astigmatic correction along two principal meridians. When the front surface remains spherical, this combination is described as a toric base curve lens—the base curve being the back surface, which is what defines the toricity. The other options don’t fit because they imply different back-surface configurations (a spherical back, multiple back curves, or a flat back) and thus don’t describe the two-meridian back curvature with a spherical front.

Two different curvatures on the back surface mean the back is toric, providing astigmatic correction along two principal meridians. When the front surface remains spherical, this combination is described as a toric base curve lens—the base curve being the back surface, which is what defines the toricity. The other options don’t fit because they imply different back-surface configurations (a spherical back, multiple back curves, or a flat back) and thus don’t describe the two-meridian back curvature with a spherical front.