In which circumstances would a base curve be specified when ordering a lens?

• A. The lens powers are very different for each eye
• B. High diopter power corrections
• C. Prescriptions for patients who have a sensitivity to base curve changes
• D. All of the above

Answer: (D)

Base curve is the curvature of the lens’s back surface and can affect how the lens sits and how it performs optically. You’d specify a base curve when the eyes require very different powers, because matching or adjusting the back curvature helps balance the image between eyes and reduces unwanted prismatic effects or differences in how each eye perceives the lens. It’s also important with high-powered corrections, where the back surface curvature has a larger impact on thickness, edge appearance, and peripheral optics, allowing the lab to select a curve that minimizes distortion and thickness while maintaining comfort. Some patients are particularly sensitive to changes in base curve, so specifying the curve helps prevent adaptation issues and unintended optical effects. For these reasons, you would specify a base curve in all of these situations.