Which statement describes water content for hydrogel and SiHy lenses?

Which statement describes water content for hydrogel and SiHy lenses?

• A. Hydrogels higher; SiHy lower
• B. Hydrogels lower; SiHy higher
• C. Both equal
• D. Hydrogels lower; SiHy lower

Answer: (A)

Water content is a measure of how much of the lens is water within the polymer matrix. Conventional hydrogel lenses are built from polymers that readily take up water, so they typically have higher water content. Silicone hydrogel lenses achieve their high oxygen permeability by incorporating silicone, which is hydrophobic, so the overall water-holding capacity of the matrix is reduced. As a result, silicone hydrogel lenses generally have lower water content than traditional hydrogel lenses. This combination gives silica-containing lenses excellent oxygen transmission with a moisture level that’s typically lower than that of hydrogels.

Water content is a measure of how much of the lens is water within the polymer matrix. Conventional hydrogel lenses are built from polymers that readily take up water, so they typically have higher water content. Silicone hydrogel lenses achieve their high oxygen permeability by incorporating silicone, which is hydrophobic, so the overall water-holding capacity of the matrix is reduced. As a result, silicone hydrogel lenses generally have lower water content than traditional hydrogel lenses. This combination gives silica-containing lenses excellent oxygen transmission with a moisture level that’s typically lower than that of hydrogels.