What does the base curve refer to in ophthalmic lenses?

What does the base curve refer to in ophthalmic lenses?

• A. The front surface curvature
• B. The back surface curvature
• C. The lens diameter
• D. The edge thickness

Answer: (B)

Base curve is the curvature of the back surface of the lens—the side that sits closest to the eye. This curve is chosen to closely match the cornea’s shape, helping the lens fit comfortably, stay well-centered, and interact properly with the tear film as you blink. The front surface curvature, lens diameter, and edge thickness are different aspects of lens design, so they aren’t what base curve describes. In practice, a too-flat or too-steep back surface can affect comfort and fit, which is why selecting the appropriate base curve matters.

Base curve is the curvature of the back surface of the lens—the side that sits closest to the eye. This curve is chosen to closely match the cornea’s shape, helping the lens fit comfortably, stay well-centered, and interact properly with the tear film as you blink. The front surface curvature, lens diameter, and edge thickness are different aspects of lens design, so they aren’t what base curve describes. In practice, a too-flat or too-steep back surface can affect comfort and fit, which is why selecting the appropriate base curve matters.