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M. Miura, M. Osako, A.E. Elsner, H. Kajizuka, K. Yamada, M. Usui; Birefringence of Intraocular Lenses . Invest. Ophthalmol. Vis. Sci. 2003;44(13):272.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose:To determine the polarization properties of intraocular lenses (IOLs) in vitro. To evaluate birefringence changes of acrylic IOLs with folding or glistening formation. Methods:The LC-PolScope Pro Imaging SystemTM (Cambridge Research & Instrumentation, Inc.) was used to measure the single-pass linear birefringence at 546.5 nm. We evaluated the linear birefringence within 3 mm of the center of IOLs in following models: MZ30BD and MA60BM (Alcon), 824C (Pharmacia), EZE55 (Bausch Lomb), VA-60CB and UV-60SB (HOYA), AR40e and SI40NB (Advanced Medical Optics), and LS106S (Santen). Refractive powers of the IOLs were the commercially available minimum power (6 - 10 diopters), 20 diopters, and maximum power (26 - 30 diopters). To evaluate the influence of folding, we tightly folded MA60BM and VA- 60CB for 30 sec, unfolded them, and measured the retardation values. To evaluate glistening, 6 pieces of MA60BM were immersed in saline solution at 50 °C for 2 hr, then removed and immersed in saline solution at 35 °C for 3 days. We selected 4 glistening micro-opacities in each IOL, and retardation values were measured at the center of the micro-opacities and their adjacent clear areas. Results:Striking polarization patterns were seen in only the 824C. Retardation values were distributed from 9.5 nm to 30.7 nm in 8 diopter model, 4.9 nm to 44.6 nm in 20 diopter model, and 2.8 nm to 64.7 nm in 30 diopter model. In other IOLs, the retardation values were ranged from 0.0 to 6.7 nm, regardless of composition. The retardation values did not differ with folding in MA60BM or VA60CB. Glistening formation significantly increased the mean retardation from 0.3 ± 0.1 to 2.1 ± 0.6 nm at the center of the micro-opacities (P < 0.001), while adjacent areas were only 0.4 ± 0.2 nm. Conclusions:The birefringence of 824C might be a possible source of error when performing polarization measurements of the fundus, and also cause small polarization-dependent focal plane changes, due to large and non-uniform retardance in the pupil plane. In other IOLs, retardation values in vitro were minimal, even with our folding procedure, and relatively uniform, even with glistening formation.
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