Which group of soft contact lens material is most likely to get lens deposits?

Which group of soft contact lens material is most likely to get lens deposits?

• A. Group 1: low water content, non-ionic
• B. Group 2: high water content, non-ionic
• C. Group 3: low water content, ionic
• D. Group 4: high water content, ionic

Answer: (D)

Deposits form mainly from tear film proteins and lipids, and how much deposits depends on material properties like surface charge and water content. An ionic surface carries a net charge that attracts oppositely charged tear proteins (for example, lysozyme), so electrostatic attraction pulls proteins onto the lens. High water content increases the lens’s permeability to water-soluble components, allowing more tear components to diffuse into and adhere to the lens matrix. Put together, a lens that is both high in water content and ionic provides the strongest combination for protein and other tear deposits to accumulate. In contrast, non-ionic surfaces lack the electrostatic pull, and low water content reduces uptake of tear components, so they deposit less.

Deposits form mainly from tear film proteins and lipids, and how much deposits depends on material properties like surface charge and water content. An ionic surface carries a net charge that attracts oppositely charged tear proteins (for example, lysozyme), so electrostatic attraction pulls proteins onto the lens. High water content increases the lens’s permeability to water-soluble components, allowing more tear components to diffuse into and adhere to the lens matrix. Put together, a lens that is both high in water content and ionic provides the strongest combination for protein and other tear deposits to accumulate. In contrast, non-ionic surfaces lack the electrostatic pull, and low water content reduces uptake of tear components, so they deposit less.