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      Effect of Ultraviolet B Radiation on the Absorption Characteristics of Various Intraocular Lenses

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          Background: The aim of this study was to determine the effect of ultraviolet B (UVB) exposure on UV filters of various intraocular lenses (IOLs). Methods: Eight samples each of the hydrophobic acrylic, hydrophilic acrylic and silicone IOLs were used. Four IOLs of each type was selected randomly as the control group while the remaining four IOLs of each type were exposed to a UVB dose of 1.4 J/cm<sup>2</sup> (2.40 mW/cm<sup>2</sup>) for 9.45 min, two times with a 4-week interval. IOLs were evaluated for any sign of opacification under microscope weekly. After a follow-up period of 16 weeks, spectrometry for UV filter absorption rates, scanning electron microscopy for deposit formation and energy dispersive X-ray analysis for elemental composition were performed for all IOLs, and findings of the control group IOLs were compared with those of the UVB-exposed IOLs. All these procedures were done at the Department of Ophthalmology, Faculty of Medicine, Dokuz Eylul University. Results: All the IOLs were free of any opacification during the follow-up period. Spectrometric analysis of their UV filters revealed a change in absorption rates in the hydrophilic acrylic and silicone IOLs compared to the control IOLs of the same type. Only the hydrophobic acrylic IOLs preserved the same UV absorption curve after UVB exposure. Conclusion: The pathogenesis of IOL opacification is still undetermined. Some reports claimed that the UV light was the responsible factor. Our experimental study revealed that high doses of UVB did not cause any opacification though they impaired the function of UV filters of the hydrophilic acrylic and silicone IOLs.

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          Most cited references 18

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          A brief photochemically induced oxidative insult causes irreversible lens damage and cataract. II. Mechanism of action.

          Using photochemically induced oxidative stress and rat lenses in organ culture with 4% O2 and 4 microM riboflavin, it has been found that the observed changes in lens parameters are, in most cases, irreversible. This has made possible the elucidation of the sequence of biological changes leading to cataract. The earliest detectable changes in lens cell biology are observed in the epithelial cell redox set point and at the DNA level in terms of DNA integrity and 3H-thymidine incorporation followed by decreased membrane transport and changes in gene expression. Significant modification in classical cataract parameters such as hydration, steady state non-protein thiol, glyceraldehyde-phosphate-dehydrogenase activity and transparency occur at later times. The data suggest a definitive pattern of lens breakdown resulting in opacity starting at the epithelial cell level and leading to subsequent fibre cell involvement.
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            Proposed pathogenesis for the delayed postoperative opacification of the hydroview hydrogel intraocular lens.

            To report the clinical, histopathologic, ultrastructural, and elemental features of 17 opacified Hydroview (Bausch and Lomb Surgical, Rochester, New York, USA) hydrogel intraocular lenses (IOL) necessitating explantation and discuss from a clinicopathologic perspective why these lenses became opacified. Interventional case series with clinicopathologic correlation. Seventeen hydrogel lenses were explanted from 17 different patients owing to decreased visual acuity or quality of vision an average of 29 months after uneventful phacoemulsification and IOL implantation and associated with a granular-appearing opacification superficially within the optic. Lenses were examined by light microscopy, transmission electron microscopy (TEM), and energy dispersion x-ray (EDX) spectroscopy. A control IOL was included in our study. All explanted lenses showed positive staining for calcium by light microscopy. Transmission electron microscopy disclosed electron-dense crystalline deposits in the superficial substance of the IOL optic. Energy dispersion x-ray spectra analyses showed the presence of calcium and phosphorus mainly in the electron-dense periphery of the deposits in all of the specimens and the presence of silicon mainly in the electron-lucent center of the deposits in the majority of the specimens. No positive staining or deposits were observed on the IOL control or in the haptics. Our study is the first to demonstrate that the calcium deposits are associated with silicon, which was presumably derived from the silicone gasket in the Surefold (Bausch and Lomb Surgical, Rochester, New York, USA) packaging system, manufactured specifically for this IOL. Silicon may act as a nidus for calcium deposition within the lens, which is consistent with our findings. There may be other factors involved, and this important clinical problem requires further study.
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              Environmental near-UV radiation and cataracts.

               S Zigman (1995)
              This report compares sunlight UV-A and UV-B fluxes in the Northeastern United States that reach the crystalline lens with thresholds that cause lens damage. The fluxes of UV-A and UV-B radiation that reach earth to penetrate the cornea and to reach the lens were calculated. Ten hours of continuous UV-A exposure or 23 min of UV-B would exceed the rabbit cornea threshold for photokeratitis. The lens threshold would be reached by 26 h of UV-A or 245 h of UV-B continuous exposure. The sequence of UV-induced damage follows: (1) UV-B photokeratitis; (2) UV-A photokeratitis; (3) UV-A lens damage; and (4) UV-B lens damage.

                Author and article information

                S. Karger AG
                December 2006
                18 December 2006
                : 221
                : 1
                : 29-35
                Departments of aOphthalmology and bDermatology, Dokuz Eylul University, cInstitute of Technology, Center for Materials Research, Izmir, Turkey
                96519 Ophthalmologica 2007;221:29–35
                © 2007 S. Karger AG, Basel

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                Page count
                Figures: 2, Tables: 1, References: 34, Pages: 7
                Original Paper


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