What characteristic is essential for the proper fitting of contact lenses?

The proper fitting of contact lenses relies heavily on the corneal curvature of the individual’s eye. This curvature affects how the lens aligns with the eye's surface and influences the overall visual acuity and comfort of the wearer. A lens that matches the corneal curvature ensures that it sits correctly on the eye, facilitating effective tear exchange and minimizing the risk of issues such as discomfort, dryness, or even corneal damage.

Finding the right lens curvature is crucial for achieving optimal centration of the lens, which impacts both vision and ocular health. Other factors, such as lens thickness and color, may have roles in specific contexts, but they do not primarily determine the fitting of the lens. The brand of the lens comes into play when factoring in design preferences or specific features but is not essential to the fit itself. Therefore, understanding and measuring the corneal curvature is the key factor for ensuring successful contact lens fitting.