Using a novel method, researchers in Canada found minimal protein impact and high efficacy of cleaning solutions when studying protein deposits on rigid gas permeable (RGP) contact lenses.  

Historically, RGP protein deposits have been difficult to measure because of test sensitivity limitations. Tackling this problem, a team led by Dr Alex Hui, head of biosciences at the Centre for Ocular Research & Education (CORE) in Waterloo undertook a unique approach. Incorporating radiolabelled lysozyme into an artificial tear solution, they were able to determine on-lens protein through radioactive counts. CORE had previously only used the technique for soft contact lens studies. 

Seven common RGP lens materials were soaked in the radiolabelled solution for 16 hours, followed by eight hours’ exposure to 3% one-step hydrogen peroxide (OSP) care solution to investigate cleaning ability.  

The researchers determined the deposits were minimal – ranging from 1.2 ± 0.2μg to 3.2 ± 0.7μg per lens – without use of a cleaning solution. Moreover, compared to using phosphate-buffered saline, the OSP solution significantly reduced the amount of radioactive lysozyme present on the majority of RGPs after 30 alternating incubating and cleaning cycles, with deposits ranging from 1.3 ± 0.1μg to 2.5 ± 0.1μg per lens. 

Dr Hui said the renewed interest in RGP lenses, sparked by their increased use in myopia management, has increased the desire for more advanced research in this domain. “CORE has built a reputation for discovering new ways to precisely assess ophthalmic devices and pharmaceuticals, and this radiolabelling technique has strong potential for other applications,” he said.  

Supported by CooperVision, the research was first presented at the 2023 Global Specialty Lens Symposium as a scientific poster, ‘The impact of RGP care solutions on ISO-measured lens parameters and the protein deposition on RGP lenses when managed with a hydrogen peroxide care solution’.