Which statement best describes the difference between aspheric and spherical contact lens designs?

• A. Spherical lenses have variable curvature for improved peripheral vision.
• B. Spherical lenses have no curvature.
• C. Aspheric lenses have variable curvature for improved peripheral vision and reduced aberrations; spherical lenses have constant curvature.
• D. Aspheric lenses are always disposable.

Answer: (C)

The main idea is how the lens surface shape affects optical quality across the eye. Spherical lenses have the same curvature from center to edge, giving a constant radius of curvature. That uniformity keeps the central vision straightforward but can leave peripheral areas more prone to spherical aberration, which can blur edges.

Aspheric lenses, on the other hand, change curvature from the center toward the edge. This variable curvature helps light rays bend more precisely across the entire pupil, reducing aberrations and often improving sharpness in the peripheral vision and overall image quality. That combination of fewer aberrations and better peripheral clarity is what makes aspheric designs different and often advantageous.

So, the idea that aspheric lenses have variable curvature for improved peripheral vision and reduced aberrations, while spherical lenses have constant curvature, best describes the difference. Statements claiming no curvature at all, or that aspheric lenses are always disposable, don’t reflect the actual designs.