Which statement best describes hydrogel lens Dk for high water content?

• A. Decreases
• B. Increases
• C. Remains constant
• D. Varies

Answer: (B)

Oxygen permeability (Dk) in hydrogel lenses rises as water content increases because more oxygen can dissolve in the water within the polymer network and then diffuse through the lens. Water-rich hydrogels provide more pathways and higher oxygen solubility, so the material becomes more permeable to oxygen. That makes the statement that Dk increases with higher water content the best description. The other options don’t fit because they imply less or no change in oxygen transfer as water content goes up, which contradicts the way water facilitates oxygen diffusion in hydrogels.