What does Dk/t represent in soft contact lens materials?

What does Dk/t represent in soft contact lens materials?

• A. Oxygen permeability
• B. Oxygen transmissibility
• C. Elastic modulus
• D. Wettability

Answer: (B)

Dk/t represents the oxygen transmissibility of a soft contact lens. It combines the material’s oxygen permeability (Dk) with the lens thickness (t), so it reflects how much oxygen can reach the cornea through the lens. A higher Dk/t means more oxygen gets through, which helps minimize corneal hypoxia; this can be achieved with a more permeable material or a thinner lens. The other properties are different: Dk is the material’s inherent ability to let oxygen pass, elastic modulus is about stiffness, and wettability describes how well the surface interacts with tear film.