Accelerated ultraviolet aging of intraocular lens optic materials: A 50 year simulation

Purpose: To introduce an updated accelerated photoaging model for application to intraocular lens (IOL) materials and to apply this model to determine the photostability of AMO® PhacoFlex® model SI-18NGB and PhacoFlex® II model SI-20NGB silicone IOL materials over a simulated 50 years of exposure. Setting: Research laboratory, AMO Surgical Products, Irvine, California, USA. Methods: Previous photoaging models and aging parameters, including intraocular exposure intensity, daily exposure duration, and acceleration exponent were critically reviewed and analyzed, and an updated model was introduced. The test specimens were continuously irradiated with ultraviolet (UV) light in a Suntest UV chamber at an intensity of 8 mw/cm2 for 86 days to simulate 50 years of in vivo exposure. The silicone lenses were evaluated for focal length, resolution, and surface integrity, while regular slabs were tested for tensile strength, elongation, hardness, contact angle, and percentage light transmission. The UV-absorption capacity was monitored using ultrathin slabs (0.127 mm). Six replicate samples were used for each determination, and a two-sided t-test with significance set at P < .05 was used to evaluate the difference before and after aging. Results: No significant difference in optical, physical, and surface properties of the lenses and lens materials was found. No change in UV-absorption capacity was observed after a simulated 50 years of accelerated photoaging. Conclusion: The AMO PhacoFlex SI-18NGB and PhacoFlex II SI-30 NGB silicone lens materials resisted UV light degradation over 50 years of simulated exposure.