Contact lenses are made from polymers, typically polymethyl methacrylate (PMMA) for hard lenses and poly hydroxyethyl methacrylate (pHEMA) for soft lenses. According to How Products Are Made, the first successful soft contact lenses were developed by chemists in the Department of Plastics at the Technical University in Prague in 1952. While the team didn’t set out to create contact lenses, they ended up creating a hydrophilic gel polymer plastic that was suitable for eye implants. One of the scientists, Otto Wichterle, began perfecting soft contact lenses in his kitchen and eventually licensed the technology to Bausch & Lomb. The company launched their Softlens in 1971 and sold about 100,000 pairs in that year.
Contact lens technology evolves
Since then, contact lenses have come a long way. Researchers are working on antimicrobial coatings for contact lenses designed to reduce eye irritation and infection. According to Vision Times, the coating is applied by simply dipping a previously cleaned lens into the solution that contains the four different components: branched polyethylenimine (bPEI), catechol, polyethylene glycol (PEG), and urea. The bPEI acts as a polymer scaffold that’s functionalized by the other components: Catechol helps the resulting coating stick to the lens surface, PEG suppresses the adhesion of microorganisms and is known to keep surfaces from fouling with proteins, and urea repels water and enhances PEG’s antimicrobial activity.
The Techtimes web site reports that contact lenses may soon become computer screens. Researchers from the Future Industries Institute of University of South Australia have developed a polymer film coating that can conduct electricity on a contact lens and possibly integrate electrical circuits safe for human wear. The team layered the lens with hydrated hydrogel substrates to deposit polymer PEDOT onto the surface engineered for both biocompatibility and conductivity. They also gave the hydrogel some plasma treatment for better adhesive quality. The ultimate goal is to produce contacts with medical benefits using nanoscale biocompatible conducting polymers grown directly on the lens.
Good lens design is all about the surface
The design of the contact lens is crucial for its usability. The lenses are in close contact with the eye, sometimes for extended periods of time, so they have to be safe and comfortable to use. Optimization of contact lens design requires the characterization of the surface. Contact lenses have been subjected to different kinds of surface treatments with the intent to make the surfaces more hydrophilic, deposit resistant, or scratch resistant. X-ray Photoelectron Spectroscopy (XPS) is the ideal analytical method for investigating elemental and chemical composition of the surface. It can also provide information about the coating layers (coating uniformity and thickness) and the interfacial chemistry. In conjunction with automated processing, it can be used to investigate coating thickness across a group of lenses.
Our next article will summarize an experiment we conducted while analyzing the surface of the contact lenses. If you can’t wait, read Analyzing Contact Lens Samples to see the results of an experiment using an XPS technology, including spectra, charts and instruments used.