Which value denotes the permeability of a contact lens?

The value that denotes the permeability of a contact lens is represented by DK. This term specifically refers to the oxygen permeability of the lens material, indicating how well oxygen can pass through the lens to reach the cornea. Oxygen is crucial for maintaining corneal health, and a higher DK value suggests better permeability, which is vital for prolonged wearing of contact lenses.

PD stands for pupil diameter and is not related to oxygen permeability. UV refers to ultraviolet protection and is concerned with blocking harmful UV rays rather than the lens's material characteristics. CL typically stands for contact lens, which does not specify any physical property like permeability. Therefore, DK is the most appropriate answer as it directly pertains to the essential factor of oxygen transmission in lens design and wear.