White light interferometry to characterize the hydrogel contact lens surface.
Maria J Giraldez1, Carlos García-Resúa, Madalena Lira
1Department of Applied Physics (Optometry Group), University of Santiago de Compostela, Santiago de Compostela, Spain. mjesus.giraldez@usc.es
Summary
Daily disposable contact lenses exhibit rougher surfaces compared to other hydrogel lenses. Analyzing larger surface areas is crucial for accurately differentiating lens characteristics.
Area of Science:
- Ophthalmic biomaterials
- Contact lens surface topography
- Surface metrology
Background:
- Understanding the surface morphology of contact lenses is essential for predicting their performance and biocompatibility.
- Conventional hydrogel contact lenses vary in their surface characteristics, influencing ocular interactions.
Purpose of the Study:
- To quantitatively and qualitatively characterize the surface morphology of four unworn conventional hydrogel contact lenses.
- To evaluate the suitability of White Light Optical Profiling (WLOP) for contact lens surface analysis.
Main Methods:
- Surface roughness of Omafilcon, Hioxifilcon-based, Nefilcon A, and Ocufilcon B lenses was assessed using WLOP.
- Key roughness parameters (Average Roughness - R(a), Root-mean-square Roughness - R(ms), Maximum Roughness - R(max)) were calculated for various surface areas.
Main Results:
- Increased measured area led to higher roughness parameter values (R(a), R(ms), R(max)) across all lens types.
- Daily disposable lenses (Nefilcon A, Ocufilcon B) demonstrated the highest surface roughness.
- Differences between lenses were less pronounced when analyzing smaller surface areas (625 and 2500 µm²).
Conclusions:
- Daily disposable hydrogel contact lenses possess a rougher surface topography.
- Analyzing larger surface areas (e.g., 67,646 µm²) is recommended for effectively distinguishing surface characteristics between different contact lens materials.
