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Updated: Jun 13, 2026
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Atomic Force Microscopy Cantilever-Based Nanoindentation: Mechanical Property Measurements at the Nanoscale in Air and Fluid
Published on: December 2, 2022
Soft contact lens surface profile by atomic force microscopy.
Maria J Giraldez1, Carmen Serra, Madalena Lira
1Department of Applied Physics (Optometry Group), University of Santiago de Compostela, Santiago de Compostela, Spain. mjesus.giraldez@usc.es
Summary
New shape parameters, kurtosis (Rku) and skewness (Rsk), offer detailed insights into contact lens surface topography. These parameters, alongside traditional roughness measures, help predict deposit formation and microbial colonization on hydrogel and silicone-hydrogel lenses.
Area of Science:
- Ophthalmic biomaterials science.
- Surface characterization techniques.
Background:
- Understanding the surface morphology of contact lenses is crucial for predicting their performance and biocompatibility.
- Conventional and silicone-hydrogel contact lenses differ in material composition and surface properties.
Purpose of the Study:
- To qualitatively and quantitatively characterize the surface morphology of unworn conventional and silicone-hydrogel contact lenses.
- To evaluate the utility of novel surface roughness parameters (kurtosis and skewness) in contact lens characterization.
Main Methods:
- Atomic force microscopy in Tapping Mode was employed to assess surface roughness.
- Key parameters measured included mean surface roughness (Ra), mean square roughness (Rms), kurtosis (Rku), and skewness (Rsk).
- Detailed surface topography mapping was performed for all lenses.
Main Results:
- Higher Ra and Rms values were observed with larger examined surface areas.
- Daily replacement lenses (nelfilcon A, ocufilcon B) had higher Ra/Rms but less spiky profiles (lower Rku).
- Comfilcon A and omafilcon A exhibited the lowest Ra/Rms and the spikiest surfaces, with most materials showing a predominance of peaks (Rsk > 0).
Conclusions:
- Kurtosis (Rku) and skewness (Rsk) provide valuable, complementary information to Ra and Rms for contact lens surface characterization.
- Detailed knowledge of contact lens surface topography aids in predicting susceptibility to deposit formation and microbial adhesion.
