A lower/higher Dk material is more scratch resistant.

A lower/higher Dk material is more scratch resistant.

• A. Higher
• B. Not sure
• C. Lower
• D. Same

Answer: (C)

Scratch resistance mainly comes from how hard and rigid the lens material is. Dk measures how much oxygen can pass through the material, not how tough the surface is. Lower Dk materials are typically more rigid and dense, so their surfaces resist scratches better because they don’t deform as easily when rubbed. Higher Dk materials, often softer and more flexible (like many silicone-containing polymers used in modern soft or silicone hydrogel lenses), tend to have softer surfaces that can show micro-scratches more readily. So, in general, a lower Dk material is more scratch resistant. Keep in mind that higher Dk improves oxygen delivery to the cornea, which is a critical clinical factor even if scratch resistance is somewhat reduced.

Scratch resistance mainly comes from how hard and rigid the lens material is. Dk measures how much oxygen can pass through the material, not how tough the surface is. Lower Dk materials are typically more rigid and dense, so their surfaces resist scratches better because they don’t deform as easily when rubbed. Higher Dk materials, often softer and more flexible (like many silicone-containing polymers used in modern soft or silicone hydrogel lenses), tend to have softer surfaces that can show micro-scratches more readily. So, in general, a lower Dk material is more scratch resistant. Keep in mind that higher Dk improves oxygen delivery to the cornea, which is a critical clinical factor even if scratch resistance is somewhat reduced.