Myopes should have a lower/higher Dk?

Myopes should have a lower/higher Dk?

• A. Lower
• B. Higher
• C. Same
• D. Not specified

Answer: (A)

The main idea is how oxygen gets to the cornea through a GP lens. Oxygen permeability (Dk) and the lens center thickness together determine how much oxygen can reach the cornea (often thought of as Dk divided by thickness, or Dk/t). If the center of the lens is thinner, more oxygen can pass through even with a lower Dk material. For myopes (minus power corrections), GP designs are typically thinner in the central zone or otherwise configured to achieve the required minus power with less material in the optical center. Because there’s less material for oxygen to diffuse through, the same or even a lower Dk material can deliver adequate oxygen to the cornea. That’s why, in this context, myopes are associated with a lower Dk choice. Keep in mind that modern GP materials often have high Dk values anyway, and the exact selection depends on lens geometry, thickness distribution, and individual corneal needs.

The main idea is how oxygen gets to the cornea through a GP lens. Oxygen permeability (Dk) and the lens center thickness together determine how much oxygen can reach the cornea (often thought of as Dk divided by thickness, or Dk/t). If the center of the lens is thinner, more oxygen can pass through even with a lower Dk material.

For myopes (minus power corrections), GP designs are typically thinner in the central zone or otherwise configured to achieve the required minus power with less material in the optical center. Because there’s less material for oxygen to diffuse through, the same or even a lower Dk material can deliver adequate oxygen to the cornea. That’s why, in this context, myopes are associated with a lower Dk choice.

Keep in mind that modern GP materials often have high Dk values anyway, and the exact selection depends on lens geometry, thickness distribution, and individual corneal needs.