A polymer-based technique to remove pollutants from soft contact lenses

TL;DR

This study introduces a novel polymer-based cleaning technique called PoPPR that effectively removes fine pollutants from soft contact lenses, outperforming traditional methods especially for nanoparticles and microplastics.

Contribution

The paper presents the PoPPR method utilizing PDMS's elastic properties as an effective alternative to rinse and rub cleaning, particularly for tiny pollutants.

Findings

PoPPR with PDMS 1:40 ratio is optimal.

PoPPR is as effective as traditional cleaning for large particles.

PoPPR significantly outperforms traditional methods for microbeads and nanoparticles.

Abstract

Purpose: To demonstrate an alternative to the rinse and rub (RR) method for cleaning pollutants from the exterior surface of soft contact lenses. This proposed technique is termed Polymer on Polymer Pollutant Removal (PoPPR), which utilizes the elastic properties of polydimethylsiloxane (PDMS) to physically remove contaminants from contact lens surfaces through non-adhesive unpeeling. Methods: Three different ratios of setting agent to polymer PDMS (1:30, 1:40, and 1:50) were evaluated using the PoPPR method against the control method of RR with a commercial multi-purpose lens cleaning solution. Three simulated pollutants of different sizes: pollen (25-40 {\mu}m), microbeads (1-5 {\mu}m), and nanoparticles (5-10 nm), were used to test the effectiveness of both cleaning methods. The fraction of pollutants removed from each contact lens was recorded and evaluated for significance. Results: PDMS 1:40 was found to be the optimal ratio for lens cleaning using the PoPPR method. For larger particles (>10 {\mu}m), no difference was observed between conventional RR and proposed PoPPR method (p > 0.05). However, the new PoPPR technique was significantly better at removing small PM2.5 particles (<2.5 {\mu}m) compared to the RR method, specifically for microbeads (p = 0.006) and nanoparticles (p < 0.001). Conclusion: This proof-of-concept work demonstrates that the PoPPR method of cleaning contact lenses is as effective as the conventional cleaning method for larger particles such as pollen. The PoPPR method is more effective at removing extremely fine particulate pollutants, including microplastics and nanoparticles. This method offers a potentially more efficient cleaning protocol that could enhance the safety, health, and comfort of contact lens users, especially those living in regions with significant air pollution.