Silicone hydrogel lenses are favored for extended wear primarily due to higher what?

• A. Oxygen permeability (Dk/t)
• B. Comfort
• C. Tear film status
• D. Wear time

Answer: (A)

Oxygen availability to the cornea is the main driver for extended wear. Silicone hydrogel lenses transmit much more oxygen to the eye than traditional hydrogel lenses, which is captured by the lens’s oxygen transmissibility, Dk/t (where Dk is the material’s oxygen permeability and t is its thickness). Because silicone hydrogels have a high Dk and can be made thinner while staying strong, their Dk/t is significantly higher. This greater oxygen delivery reduces corneal hypoxia, edema, and related complications during overnight wear, making extended wear safer and more comfortable. While comfort and tear film status matter for daily wear, the fundamental enabling factor for extended wear is the higher oxygen permeability through the lens.