Nanostructural properties of intraocular lenses (IOLs) – atomic force microscopy (AFM) and Fourier transform infrared spectroscopy (FTIR) investigations

Purpose To investigate and analyze surface of explanted intraocular lenses (IOL-s), by means of the Atomic Force Microscope (AFM) and Fourier transform infrared spectroscopy (FTIR). Methods Eight dry IOL-s (acrylic: SN60AT – 3 pieces, SA60AT , CZ70BD; silicone: CLRFLXC; “hard”: AJPR,CP65T), and four hydrophilic acrylic IOL-s (AC-IOL and PC- IOL, both: naive and removed during keratoplasty) were imaged (topography and phase) with AFM. AFM is used to investigate, at nanoscale, the surfaces’ topography and some nanomechanical properties (eg. elasticity, hardness) of materials in medicine. The samples can be investigated in quasi-physiological conditions, usually no damaging preparation is required. For the acrylic and “hard” lenses the granular nanostructure is observed. The roughness of the lenses’ surfaces can be then assessed. The silicone lens is soft: the forces of nanonewtons applied during imaging cause strong deformations of the material. Results Nanomechanical properties of PC-IOL lens are not uniform. This may be advantageous for its calcification: for the lens of the same type removed during keratoplasty strong calcification is observed. For SN60AT lens the influence of the application process (folding) on its nanostructure is tested. The observed structural nano-defects are permanent, they can occur during folding or can be caused by the used equipement. The similar nano-deformations are observed for the removed AC-IOL lens. Conclusion AFM and FTIR showed to be a high-resolution imaging tool for the scanning of surface IOL.