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M.K. Green, S. Porbandarwalla, N. Kumar, V.L. Dougherty, C.P. Mullens, R.D. Glickman, S.B. H. Bach, W.E. Sponsel; Can Phthlates Be Released From Intraocular Lenses? . Invest. Ophthalmol. Vis. Sci. 2006;47(13):608.
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Foldable acrylic intraocular lenses (IOLs) have an excellent safety record. Rarely, however, as a result of injection, folding, or manufacturing problems, a lens may crack and require removal. In the only two cases in our experience in which an acrylic lens required removal, we carefully bisected the lens in situ and removed the fragments carefully to minimize intraocular trauma. Subsequently, both patients demonstrated long–term uveitis, the protracted character of which seemed disproportionate to any surgical insult. We thus sought a physical or chemical basis for chronic inflammation associated with a brief intraocular exposure to a transected acrylic lens.
We tested four commercially available acrylate–methacrylate copolymer lenses. Lenses were cut with a surgical scissors to check for ejection of physical debris. Chemical analysis of the supernatant was carried out with gas chromatography electron impact ionization mass spectrometry (GC–EI–MS), to determine if potentially irritating substances were liberated. Lens fragments were soaked in a variety of solvents, including methylene chloride (MeCh) and deionized water (DIW). The structures of liberated chemical compounds were confirmed with nuclear magnetic resonance spectroscopy (NMR).
Videomicroscopy demonstrated that no solid lens fragments were released during cutting. In both MeCh and DIW bis–2–ethylhexyl phthalate was identified with GC–EI–MS, and the structure confirmed with NMR. The concentration of phthalate eluted into ionized water (∼35 µg/ml) was comparable to that liberated by methylene chloride (∼50 µg/ml). A bioassay was done, exposing cultured human lens epithelial cells to the identified phthalate to evaluate cell viability. The results indicated cell viability was reduced at phthalate concentrations as low as 20 µg/ml.
Foldable injectable IOLs have been a boon for ophthalmic practice. However, if replacement of a defective lens becomes necessary, bisection of the lens in situ should be avoided, as a bisected IOL may release phthalates into the eye. Because bis–2–ethylhexyl phthalate was isolated in DIW, it could be released into the aqueous and affect intraocular tissues. The emerging awareness of the toxicity of low–level phthalates in a variety of biological settings warrants further studies of the interaction of plasticizers with intraocular tissue.
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