Microscopic observation of unworn siloxane-hydrogel soft contact lenses by atomic force microscopy

• Published in: Journal of biomedical materials research. Part B, Applied biomaterials Vol. 76B; no. 2; pp. 412 - 418
• Main Authors: González-Méijome, José M., López-Alemany, Antonio, Almeida, José B., Parafita, Manuel A., Refojo, Miguel F.
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 01.02.2006
• Subjects: atomic force microscopy; Contact Lenses, Hydrophilic; Humans; Hydrogel, Polyethylene Glycol Dimethacrylate - chemistry; Hydrogel, Polyethylene Glycol Dimethacrylate - metabolism; Materials Testing; Microscopy, Atomic Force; siloxane-hydrogel contact lenses; Siloxanes - chemistry; Siloxanes - metabolism; Surface Properties; surface roughness; Wettability
• ISSN: 1552-4973; 1552-4981
• DOI: 10.1002/jbm.b.30387

In the present study, samples of lotrafilcon A, balafilcon A, and galyfilcon A contact lenses were observed by atomic force microscopy (AFM) in tapping mode at areas ranging from 0.25 to 400 μm2. Mean roughness (Ra), root‐mean‐square roughness (Rms) and maximum roughness (Rmax) in nanometers were obtained for the three lens materials at different magnifications. The three contact lenses showed significantly different surface topography. However, roughness values were dependent of the surface area to be analyzed. For a 1 μm2 area, statistics revealed a significantly more irregular surface of balafilcon A (Ra = 6.44 nm; Rms = 8.30 nm; Rmax = 96.82 nm) compared with lotrafilcon A (Ra = 2.40 nm; Rms = 3.19 nm; Rmax = 40.89 nm) and galyfilcon A (Ra = 1.40 nm; Rms = 1.79 nm; Rmax = 15.33 nm). Ra and Rms were the most consistent parameters, with Rmax presenting more variability for larger surface areas. The higher roughness of balafilcon A is attributed to the plasma oxidation treatment used to improve wettability. Conversely, galyfilcon A displays a smoother surface. Present observations could have implications in clinical aspects of siloxane–hydrogel contact lens wear such as lens spoliation, resistance to bacterial adhesion, or mechanical interaction with the ocular surface. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2006