Plasma-induced surface modifications on silicone intraocular lenses: chemical analysis and in vitro characterization.

In contrast to the high standard of intraocular lens implantation today, lens fixation and the occurrence of secondary opacifications are still not satisfactory. We are working on an implant that builds a stable connection to the surrounding lens-capsule. Disc-shaped lenses made of poly(dimethylsiloxane) were treated with different kinds of plasma to bring functional groups to the surface. This allows further macromolecular coating. The results of the surface modifications were characterized by electron spectroscopy for chemical analysis, scanning electron microscopy, Fourier transform infrared spectroscopy and cell culture experiments. O2 plasma induces a rapid increase of functional groups on the lens surface. CO2 plasma has to be used for longer treatment periods to achieve the same increase, but as SEM shows, did not lead to surface damage up to periods of 300 s. Using O2 plasma for longer than 60 s, a crack formation occurred. Therefore, CO2 plasma may be a more effective and sensitive tool in grafting functional groups to the surface.