Does a GP lens with thin central thickness have greater oxygen transmission?

• A. Yes
• B. No
• C. Only with certain materials
• D. Depends on environmental conditions

Answer: (A)

Oxygen transmission through a GP lens depends on both the material’s permeability (Dk) and the thickness of the lens (t). The key quantity is Dk/t, the oxygen transmissibility. When the central thickness is thinner, the diffusion path for oxygen is shorter, so for the same material (same Dk) the Dk/t value increases. This means more oxygen can reach the corneal surface per unit time, reducing hypoxic stress. So, a rigid gas permeable lens with a thinner central thickness will have greater oxygen transmission, all else equal.