What does the diameter of a contact lens indicate?

The diameter of a contact lens indicates the size of the lens across its widest point, which is essential for proper fitting and comfort. A correctly sized lens ensures that it remains centered on the cornea and provides optimal vision. If the diameter is too small, the lens may not cover the cornea adequately, leading to discomfort and inadequate vision. Conversely, if it is too large, the lens could irritate the surrounding tissues or cause movement on the eye, which can also affect vision.

Understanding the diameter is crucial for ensuring that the lens adheres properly to the eye and provides the intended corrective effect. Other options relate to different aspects of the lens, such as thickness, prescription strength, or curvature, but do not define what the diameter specifically indicates.