Adsorption and removal of protein bound to hydrogel contact lenses

Tear film proteins are known to adsorb to new hydrogel contact lenses. Using a radioiodine tracing technique, proteins were shown to adsorb to contact lens surfaces. The quantity of protein adsorbed to the contact lenses within 2 to 4 h was 1 to 3 micrograms/lens. The degree of protein adsorption varied from lens-to-lens depending in part on the water content of the lens. High water content ionic lenses bound the most protein, whereas lower water content and nonionic lenses bound less protein. Enzyme cleaning of the protein-coated contact lenses removed about 75% of the adsorbed protein. When the enzyme-cleaned lenses were reincubated with protein, similar quantities were quickly readsorbed within a similar period of time. The rate of readsorption appeared to vary with the type of enzyme used to clean the lenses. Hydrogel lenses adsorb protein from the tear film rapidly and irreversibly. Cleaning the lenses has only a partial and temporary effect on the bound protein. The lens-bound proteins could become partly denatured during their binding to the lenses. These observations suggest a possible role for such proteins in ocular sensitivity to contact lenses.