Which statement describes the coefficient of friction for hydrogel and SiHy lenses?

Which statement describes the coefficient of friction for hydrogel and SiHy lenses?

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

Answer: (B)

Friction at the lens–eye interface is mainly governed by surface wettability and the tear film lubrication that covers the lens. Hydrogels are highly hydrophilic, meaning they attract and retain water, creating a very lubricious surface that reduces resistance to sliding during blinking. Silicone hydrogel lenses, while excellent for oxygen permeability, incorporate silicone which makes the surface more hydrophobic and can reduce tear film spreading on the lens surface. This leads to higher resistance to sliding, i.e., a higher coefficient of friction. So the best description is that hydrogel lenses have lower friction, while silicone hydrogel lenses have higher friction. If a statement claimed both have higher friction or that hydrogel friction is higher, it wouldn’t align with the differences in surface chemistry and lubrication that typically distinguish these materials.

Friction at the lens–eye interface is mainly governed by surface wettability and the tear film lubrication that covers the lens. Hydrogels are highly hydrophilic, meaning they attract and retain water, creating a very lubricious surface that reduces resistance to sliding during blinking. Silicone hydrogel lenses, while excellent for oxygen permeability, incorporate silicone which makes the surface more hydrophobic and can reduce tear film spreading on the lens surface. This leads to higher resistance to sliding, i.e., a higher coefficient of friction.

So the best description is that hydrogel lenses have lower friction, while silicone hydrogel lenses have higher friction. If a statement claimed both have higher friction or that hydrogel friction is higher, it wouldn’t align with the differences in surface chemistry and lubrication that typically distinguish these materials.