Which of the following is a main reason to choose an aspheric lens over a spherical lens?

• A. Lower cost
• B. Good optics
• C. Increased weight
• D. Lack of progressive power optics

Answer: (B)

Reducing spherical aberration to improve optical quality is the main reason to choose an aspheric lens over a spherical lens. A spherical surface bends light the same amount across its radius, so edge rays don’t come to the same focus as central rays, causing blur and reduced sharpness—especially at higher powers or toward the edge of the lens. An aspheric surface changes curvature from center to edge, guiding peripheral rays to the same focal point as central rays. The result is crisper vision, better contrast, and fewer edge distortions, with the added benefit that strong prescriptions can yield a thinner, lighter lens. Cost and manufacturing complexity can be factors, and progressive versus single-vision design is separate, but the core reason remains the improved optics from correcting spherical aberration.