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 is all about how much oxygen can get through the lens to the cornea in real wear. Dk is the material’s intrinsic oxygen permeability, but when a lens sits on the eye, its thickness matters too. Dk/t combines those factors by dividing the material’s permeability by the lens thickness, giving the actual amount of oxygen that passes through per unit area per unit time through the lens. Clinically, a higher Dk/t means better oxygen delivery to the cornea and less risk of hypoxia. The other terms describe different properties: permeability alone refers just to the material, elastic modulus relates to stiffness, and wettability is about how the surface interacts with tear film. So Dk/t best represents how much oxygen the lens transmits to the eye.

Dk/t is all about how much oxygen can get through the lens to the cornea in real wear. Dk is the material’s intrinsic oxygen permeability, but when a lens sits on the eye, its thickness matters too. Dk/t combines those factors by dividing the material’s permeability by the lens thickness, giving the actual amount of oxygen that passes through per unit area per unit time through the lens. Clinically, a higher Dk/t means better oxygen delivery to the cornea and less risk of hypoxia. The other terms describe different properties: permeability alone refers just to the material, elastic modulus relates to stiffness, and wettability is about how the surface interacts with tear film. So Dk/t best represents how much oxygen the lens transmits to the eye.