Susceptibility of Various Intraocular Lenses to Nd: YAG Laser In Vitro

Wee, Won Ryang; Chung, Eui Sang; Kim, Dong Myung; Lee, Jin Hak; Chang, Bong Leen

Abstract

The purpose of this study was to evaluate the susceptibility of various intraocular lenses(IOLs) of different optic material to Nd:YAG laser in vitro. Four models of IOLs manufactured by different companies were selected and ten IOLs for each model were used for this study. Two models had lathe-cut polymethylmethacrylate(PMMA) optic, one silicone compound optic, and one acrylate/methacrylate copolymer optic. Q-switched Nd: YAG laser(7901 Nd-YAG laser, Coherent, Palo Alto, CA, USA) was used. The He-Ne aiming beam was focused on the posterior surface of optic, 2mm apart from the center of optic, and sixteen shots were applied to each optic with energy levels ranging from 0.3 to 2.0mJ with increment of 0.1 or 0.2mJ in a circular pattern. The spots were examined under phase contrast microscope and scanning electron microscope. The averages(+/-SD) of energy threshold at which damage was detected were 0.49+/-0.12mJ in silicone compound optic, 0.67+/-0.19mJ in acrylate/methacrylate copolyer optic, and 0.72+/-0.11mJ and 0.89+/-0.09mJ in lathe-cut PMMA optics. All interclass differences were statistically significant except the difference between lathe-cut PMMA optic with lower damage threshold and acrylate/methacrylate copolymer optic(Mann-Whitney test, p<.05). In conclusion, silicone compound and acrylate/methacrylate copolymer optics are more susceptible to Nd:YAG laser than PMMA optic in vitro and this suggests that in patients with high risk of developing severe posterior capsular opacification after cataract surgery, implantation of IOLs with PMMA optic is preferable and early Nd:YAG laser posterior capsulotomy with low energy is recommended in cases of implantation of foldable IOLs.