Microscopic investigations of surface texture of siloxane-hydrogel contact lenses

Purpose: The objective of this article was to investigate experimentally the 3-D surface of unworn/worn contact lenses (CLs) using stereometric analysis applied to atomic force microscopy (AFM) micrographs. Materials and methods: Fractal and stereometric analyses were applied in micromorphology investigations of siloxane-hydrogel CLs made of Filcon V. Qualitative and quantitative study of surface texture was made using statistical parameters of 3-D surface roughness, according with ISO 25178-2: 2012 for: CL rins (unworn CLs taken from the blister and rinsed with deionized water); CL worn-smooth (worn for 8 h and presenting a smooth-type morphology), and CL worn-sharp (worn for 8 h and presenting a sharp-type morphology). Results: Fractal analysis reveals fractal nature at nanometer scale of all surface samples. The fractal dimensions determined by enclosing boxes method of the studied samples are: D f = 2.25 ± 0.01 for CL rins , D f = 2.29 ± 0.01 for CL worn-smooth and D f = 2.40 ± 0.01 for CL worn-sharp . Conclusions: Surface statistical parameters can be deduced by analyses of micromorphology and fractal structure of the 3-D surface of CLs. The variation of these parameters provides quantitative information on the effects of wear, such as in the cases of the two morphologies which can be found after 8 h wear of Filcon V CLs. POLYM. ENG. SCI., 59:E442–E451, 2019. © 2019 Society of Plastics Engineers.