What does it mean if a lens is fit "on K"?

When a lens is fit "on K," it signifies that the base curve of the contact lens aligns with the flattest curvature measurement of the cornea, referred to as the K reading or keratometry reading. The K readings provide crucial information about the cornea's shape, which directly influences how a contact lens will sit on the eye.

Fitting a lens on this reading ensures that the contact lens is designed to match the cornea's geometry, leading to a more stable and comfortable fit. This alignment can help maintain proper lens positioning, enhance visual acuity, and promote corneal health, as an appropriate fit minimizes the risk of complications such as corneal abrasion or discomfort.

The other choices do not accurately represent the concept of fitting on K. They either misinterpret the relationship between lens curvature and the cornea or suggest scenarios that are not aligned with standard contact lens fitting practices.