Which factor best explains why soft lenses typically have a limited number of base curves?

Which factor best explains why soft lenses typically have a limited number of base curves?

• A. The base curve radius of a soft lens fits a wide range of corneas
• B. Manufacturers produce only a few curves due to demand
• C. The base curve of a soft lens can be fine-tuned during manufacturing but limited to a few standard curves
• D. Lenses are designed for long-term wear only

Answer: (A)

Soft lenses use a highly flexible material that can conform to the corneal shape as the tear film cushions and supports the lens. Because of that adaptability, a relatively small set of standard base curve radii can fit the vast majority of eyes. The fit is achieved not only by the curve but also by diameter and lens power, so manufacturers don’t need dozens of unique base curves. In contrast, more rigid lenses require a wider range of base curves to match the precise curvature of the cornea, which is why this limited curve choice is particularly characteristic of soft lenses.

Soft lenses use a highly flexible material that can conform to the corneal shape as the tear film cushions and supports the lens. Because of that adaptability, a relatively small set of standard base curve radii can fit the vast majority of eyes. The fit is achieved not only by the curve but also by diameter and lens power, so manufacturers don’t need dozens of unique base curves. In contrast, more rigid lenses require a wider range of base curves to match the precise curvature of the cornea, which is why this limited curve choice is particularly characteristic of soft lenses.