Which statement is true about hydrogel lenses?

Which statement is true about hydrogel lenses?

• A. Hydrogel lenses were originally made from HEMA monomers cross-linked with EDMA.
• B. Hydrogel lenses are made of glass.
• C. Hydrogel lenses are made only of silicone.
• D. Hydrogel lenses do not interact with water.

Answer: (A)

Hydrogel lenses are soft, water-absorbing polymer networks. The classic makeup uses hydroxyethyl methacrylate (HEMA) monomers that are cross-linked with a small molecule such as ethylene glycol dimethacrylate (EDMA). This cross-linked structure swells in water, yielding a flexible, comfortable lens that also allows oxygen to reach the cornea. They are not made of glass, and they are not made only of silicone—though silicone-containing variants exist, the traditional hydrogel is a hydrated polymer, not a solid silicone or glass. They do interact with water, which is essential to their softness, transparency, and oxygen permeability.

Hydrogel lenses are soft, water-absorbing polymer networks. The classic makeup uses hydroxyethyl methacrylate (HEMA) monomers that are cross-linked with a small molecule such as ethylene glycol dimethacrylate (EDMA). This cross-linked structure swells in water, yielding a flexible, comfortable lens that also allows oxygen to reach the cornea.

They are not made of glass, and they are not made only of silicone—though silicone-containing variants exist, the traditional hydrogel is a hydrated polymer, not a solid silicone or glass. They do interact with water, which is essential to their softness, transparency, and oxygen permeability.