Towards improving the biocompatibility of prosthetic eyes

Prosthetic eyes are currently manufactured using Poly(methyl methacrylate) (PMMA) which is not an ideal material because it is hydrophobic. While significant research has investigated the benefits of hydrophilic materials for contact lenses, no such research has been carried out on hydrophilic materials for prosthetic eyes until now. In this study, different derivatives of Poly(ethylene glycol) (PEG) monomer and methyl methacrylate (MMA) monomer were grafted to PMMA using copolymerisation. The resulting matrixes were evaluated by water contact angle measurement, 24 h water absorption testing, and colour-difference measurement when exposed to ultraviolet light. The contact angle and water absorption results indicated that ethylene glycol dimethacrylate (EGDMA) grafted PMMA matrix had a better hydrophilic performance than the other matrixes tested. EGDMA is already a minor constituent of the PMMA matrix currently used for manufacturing prosthetic eyes but when the proportion of EGDMA monomer to MMA monomer used in the manufacturing process was increased to 50/50 the hydrophilicity of the matrix was significantly improved. EGDMA-grafted PMMA is inexpensive and comes as a liquid monomer that is easily mixed with the PMMA monomer that ocular prosthetists are familiar with. The mixture requires no special handling beyond the normal safety precautions that apply when using PMMA monomers. In-vitro testing shows that EGDMA-grafted PMMA significantly improves the wettability of PMMA currently used for the manufacture of prosthetic eyes and has the potential to significantly improve wearing comfort and socket health.