Which value indicates the permeability of a contact lens?

The value that indicates the permeability of a contact lens is known as DK. This designation represents the oxygen permeability of the lens material, which is crucial for maintaining corneal health during lens wear. Oxygen is essential for the metabolic processes of the cornea, which does not have its own blood supply.

The DK value indicates how much oxygen can pass through a unit thickness of contact lens material over a specified period and is typically measured in units of barrers. A higher DK value suggests that more oxygen can reach the eye, reducing the risk of hypoxia-related complications such as corneal swelling or discomfort associated with extended wear contact lenses.

Other terms like PC (usually referring to near point convergence), HR (which might refer to heart rate, irrelevant in this context), and TP (which stands for tear film break-up time), do not pertain to the permeability of contact lenses and thus are not relevant to this question.