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M. Lombardo, G. Carbone, G. Lombardo, M. P. De Santo, R. Barberi; Atomic Force Microscopy Analysis of Surface Adhesive Properties of Intraocular Lenses. Invest. Ophthalmol. Vis. Sci. 2009;50(13):2413.
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© ARVO (1962-2015); The Authors (2016-present)
To analyze the surface adhesiveness of various types of intraocular lens (IOL) using Atomic Force Microscopy (AFM).
The surface adhesiveness of poly-methyl-methacrylate (PMMA), silicone, hydrophilic acrylic and hydrophobic acrylic IOLs was investigated using AFM. Analysis was performed in liquid environment with a commercial instrument (NanoScope III, Veeco, Sunnyvale, CA) in the Force-vs-distance (f-d) mode. Measurements of the adhesive force between the tip and the lens optic surface were acquired with rectangular silicon cantilevers of nominal elastic constant of 10 Newton/meter (N/m). The nominal value of the cantilever tips radius of curvature was 1 µm and the scanning speed during the acquisitions were in the range 2-50 nm/s.
Multiple f-d curves were recorded on different areas of the central posterior optic surface and always showed the same features, indicating that the lens surface was homogeneous as physico-chemical properties. Moreover, for each position, no modification in the adhesion was seen with repeated contacts and high-resolution images confirmed that the IOL surface morphology was not modified nor damaged during the course of the force measurements. The adhesion force measurements revealed statistically different characteristics for the various type of lenses (P<0.001; ANOVA). The acrylic hydrophobic lens exhibited the mean largest adhesive force (283.7 ± 0.14 nanoNewton, nN) followed by the acrylic hydrophilic (84.7 ± 0.94 nN), PMMA (45.7 ± 0.47 nN) and silicone lenses (2.10 ± 0.01 nN).
The properties of the biomaterials used to manufacture IOLs are important factors as they can influence the incidence and severity of the posterior capsule opacification (PCO). AFM showed to be an effective and accurate tool for analyzing IOLs and may deliver relevant information on the biocompatibility of implantable biomaterials that have to be introduced in the ophthalmologic surgical practice. While further studies are necessary to elucidate the mechanism of PCO development and the interface interactions between the IOL and capsule, the results from this study may enhance the theory of manufacturing more adhesive materials to minimize PCO rate after cataract surgery.
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