Abrasive cleaners can cause which changes to GP lenses?

• A. Increases CT
• B. Creates small surface scratches, can reduce CT and create minus power
• C. Changes in refractive index
• D. No changes

Answer: (B)

Abrasive cleaners physically wear on the lens surface, producing micro-scratches and roughness. GP lenses depend on smooth, precisely curved surfaces, so any surface damage can alter the optical contour. When material is worn from the center or the surface is scratched, the central thickness can decrease and the local curvature can shift enough to introduce a small minus power. The refractive index of the lens material isn’t changed by cleaning, so the main effects are surface geometry changes and slight power shifts caused by that altered contour. That’s why abrasive cleaners can cause small surface scratches, reduced central thickness, and a minus component to the power.