FDA group 2 classification: Which description best fits Group 2?

FDA group 2 classification: Which description best fits Group 2?

• A. Low Water Polymer, Nonionic Polymer
• B. High Water Content, Nonionic Polymer
• C. Silicone Hydrogels
• D. Low Water Content, Ionic Polymer

Answer: (B)

In this classification, lenses are sorted by two properties: how much water they contain and whether the polymer carries ionic (charged) groups. The best fit for Group 2 is a material with high water content and a nonionic polymer. High water content improves oxygen transmission, since water pathways help deliver oxygen to the cornea. Being nonionic means the polymer surface lacks charged groups, which reduces specific interactions with charged tear components like certain proteins and mucins. So you get a lens that can deliver good oxygen due to its hydration, while maintaining a relatively neutral surface chemistry that influences deposition and wettability in a distinct way from ionic or low-water materials. The other options describe combinations that map to different groups—low water content ones or ionic ones, or silicone-hydrogel families, which aren’t described by this particular group’s high water, nonionic profile.

In this classification, lenses are sorted by two properties: how much water they contain and whether the polymer carries ionic (charged) groups. The best fit for Group 2 is a material with high water content and a nonionic polymer. High water content improves oxygen transmission, since water pathways help deliver oxygen to the cornea. Being nonionic means the polymer surface lacks charged groups, which reduces specific interactions with charged tear components like certain proteins and mucins. So you get a lens that can deliver good oxygen due to its hydration, while maintaining a relatively neutral surface chemistry that influences deposition and wettability in a distinct way from ionic or low-water materials. The other options describe combinations that map to different groups—low water content ones or ionic ones, or silicone-hydrogel families, which aren’t described by this particular group’s high water, nonionic profile.