Optical and mechanical characterization of UV-irradiated hydrophobic acrylic intraocular lenses

Hydrophobic acrylic intraocular lenses (IOLs) undergo significant optical, chemical, surface, and mechanical changes upon prolonged ultraviolet (UV) exposure. We assessed a commercial hydrophobic acrylic IOL using an accelerated UV protocol (1-25h) and a multimodal workflow combining UV-Vis spectrophotometry, ATR-FTIR spectroscopy, contact-angle measurements, and Shore C hardness testing. UV-Vis spectroscopy revealed up to a 40% decrease in UV transmittance after 25h, and a 36-50% increase in absorbance extending into the short-wavelength visible region, consistent with the formation of additional absorbing centers that may influence long-term optical quality. ATR-FTIR analyses indicated photochemical modifications in the acrylate backbone compatible with photo-oxidation, including chain scission and ester rearrangement. Wettability showed a transient hydrophobic shift with peaks at approximately 3h for both test liquids, with a more pronounced hydrophobic shift for the glucose solution, followed by a return to baseline by 25h, suggesting competing surface reorganization and oxidation processes. Shore C hardness increased from 63.0 to 73.1 after 25h, indicating UV-induced stiffening. To our knowledge, this is the first study to simultaneously report these four modalities together for accelerated UV aging of a single hydrophobic acrylic IOL model.