Evaluation of in vitro glistening formation in hydrophobic acrylic intraocular lenses

PURPOSE: To evaluate the impact of continuous manufacturing process improvements on glistening formation in AcrySof hydrophobic acrylic intraocular lenses (IOLs) by comparing lenses manufactured in 2003 with lenses manufactured in 2012. METHODS: Glistenings were experimentally created as aqueous-filled microvacuoles utilizing an accelerated laboratory method by immersing the lens in water at 45°C for 24 hours and then reducing the temperature to 37°C for 2.5 hours. To determine the impact of continuous improvements on glistening formation, AcrySof IOLs (Alcon Laboratories, Inc) Model SB30 AL manufactured in 2003 were compared with AcrySof IOLs Model SN60 WF manufactured in 2012. RESULTS: Glistenings were present in all lenses after the accelerated microvacuole test method. The mean microvacuole density for IOLs manufactured in 2003 was 315.7 microvacuoles per square millimeter (MVs/mm(2)) with a glistening severity less than 100 MVs/mm(2) in 1.0% of the IOLs. The mean microvacuole density for IOLs manufactured in 2012 was 39.9 MVs/mm(2) with a glistening severity less than 100 MVs/mm(2) in 95.2% of the IOLs. Laboratory-induced microvacuole density was significantly lower in IOLs manufactured in 2012 (mean 39.9 MVs/mm(2)) relative to IOLs manufactured in 2003 (mean 315.7 MVs/mm(2)) as indicated by the Wilcoxon test of significance (P < 0.0005). CONCLUSION: AcrySof IOLs recently manufactured in 2012 demonstrated a significant reduction in glistening density (87% reduction in mean density) as a result of continuous manufacturing process improvements compared with IOLs manufactured in 2003.