Analysis of intraocular lens surface adhesiveness by atomic force microscopy

PURPOSE: To analyze intraocular lens (IOL) optic surface adhesiveness using atomic force microscopy (AFM). SETTING: LiCryL Laboratory, University of Calabria, Rende, Italy. METHODS: The surface adhesive properties of poly(methyl methacrylate) (PMMA), silicone, hydrophilic acrylic, and hydrophobic acrylic IOLs were evaluated by AFM. Analysis was performed at room temperature (21 degrees C) in a liquid environment using the force-versus-distance mode of a commercial instrument (NanoScope III). Measurements were acquired with rectangular silicon cantilevers of a nominal elastic constant of 10 Newton/m. The nominal value of the tip's radius of curvature was 1 mu m, and the scanning speed during the acquisitions ranged from 10 to 400 nm/s. RESULTS: The adhesion force measurements showed different characteristics for the various types of IOLs (P<.001, analysis of variance). The hydrophobic acrylic IOL had the largest mean adhesive force (283.75 nanoNewton [nN] +/- 0.14 [SDI) followed by the hydrophilic acrylic (84.76 +/- 0.94 nN), PMMA (45.77 +/- 0.47 nN), and silicone (2.10 +/- 0.01 nN) IOLs. CONCLUSIONS: The surface properties of the biomaterials used to manufacture IOLs are important because they can influence the incidence and severity of posterior capsule opacification (PCO). Although further studies are necessary to elucidate the mechanism of PCO development and the interface interactions between the IOL and capsule, the results in this study may bolster the theory of manufacturing more-adhesive materials to prevent PCO.