The consequences of removing fluorinated compounds from rigid contact lenses

Fluorine free analogues of three commercially available rigid contact lens materials were prepared by replacing the fluorinated component, hexafluoroisopropyl methacrylate (HFPM), with the widely used, non-fluorinated monomers methyl methacrylate (MMA) and 3-methacryloxypropyltris-(trimethylsiloxy)silane (TRIS). The properties of the commercial materials and analogues were measured and compared. The oxygen permeabilities of the MMA analogues were found to be significantly lower than those of the commercial materials, decreasing by 87 % on average, while the TRIS analogues lacked sufficient hardness, dimensional stability and lipid deposit resistance to be viable for use in rigid contact lenses. Analogues prepared using a 1:1 mixture of MMA and TRIS had the best overall combination of properties, but were still on average 47 % less permeable to oxygen and also significantly less resistant to lipid deposition. The analogues prepared in this study did not adequately replicate the performance of marketed, fluorine containing rigid contact lens materials. These observations give an indication of the challenges that would face contact lens material manufacturers in preparing rigid lens polymers without the use of fluorinated species. A reduction in effectiveness would be almost inevitable, and would be expected to have a negative impact on the safety and eye health of rigid contact lens patients.

Automated summary

Fluorine-free analogues of three commercially available rigid contact lens materials were prepared and compared to evaluate their performance. The replacement of hexafluoroisopropyl methacrylate with non-fluorinated monomers resulted in reduced oxygen permeabilities and inadequate hardness, dimensional stability, and lipid deposit resistance. The best overall properties were achieved with a 1:1 mixture of methyl methacrylate and 3-methacryloxypropyltris-(trimethylsiloxy)silane, but they still exhibited lower oxygen permeability and lipid deposition resistance. These findings highlight the challenges in developing rigid lens polymers without the use of fluorinated species and the potential negative impact on safety and eye health.