Detection, removal, and effect of unpolymerized methylmethacrylate in intraocular lenses

Gas-liquid chromatography, infrared spectroscopy, or Raman spectroscopy were used to determine the level of monomer in intraocular lenses and in the preforms used in each step of the manufacturing process. Heating, lathing, molding, and grinding caused an increase in monomer content, presumably the result of depolymerization. The tendency of methylmethacrylate to volatilize, repolymerize, or dissolve precludes high monomer contents from persisting in intraocular lenses. Vacuum ovens or water baths significantly reduced the monomer content to levels of 0.5% or less. Lenses with a monomer content higher than that found in currently available commercial lenses had no effect on rabbit kidney cell cultures. Lens fragments with a similarly elevated monomer content were indistinguishable from lenses with a low monomer content in rabbit eyes. According to these data, monomer does not appear to be a toxic agent in currently available intraocular lenses.