What does 'Base Curve' indicate in the context of contact lenses?

The term 'Base Curve' refers to the curvature of the contact lens. This measurement is crucial because it affects how the lens sits on the eye and contributes to the overall fit and comfort for the wearer. The base curve is determined by the shape of the cornea and is designed to provide a snug yet comfortable fit against the eye, allowing for optimal vision correction and minimizing movement of the lens during activities. A proper base curve helps in maintaining tear film stability and reduces the risk of complications such as discomfort or irritation.

For context, the other choices relate to different aspects of vision correction and lens design but do not capture the specific definition of 'Base Curve.' For example, while the distance around the lens and the center point for lens correction are related to fitting and function, they do not address the curvature aspect directly, which is essential for ensuring that the contact lens conforms appropriately to the natural shape of the eye. Similarly, the power needed for astigmatism pertains to prescription details rather than the geometric characteristics defined by the curvature.