Reducing the amount of monomers in intraocular lenses through sterilization by gamma radiation.

Sterile inflammatory reactions of varying degrees are a rare, but not uncommon, complication after intraocular lens implantation. At present we still do not know the cause of these processes, but we consider two chemical substances contained in the lens at least as risk factors for them: monomeric methyl methacrylate, which is present in any lens made from polymethyl methacrylate (Perspex), and ethylene oxide, an extremely toxic agent, which is absorbed by the lens during sterilization with this gas. Gas chromatographic investigations show that under sterilization of intraocular lenses by 60Co radiation the amount of monomeric methyl methacrylate in the lens can be reduced drastically. Also, any contamination of the lens by ethylene oxide is avoided. Therefore, at least two important arguments speak in favor of this alternative sterilization technique.