Effect of Rewetting Drops Use on Comfort and Protein Deposition of Silicone Hydrogel (Focus Night&Day) Contact Lenses

Abstract

Abstract: : Purpose:Silicone hydrogel (SH) contact lenses provide sufficient corneal oxygenation to allow for edema–free overnight wear. However, symptoms of dryness with SH lenses are still prominent in wearers of these lenses and previous work by our group has demonstrated that their relatively hydrophobic surface can result in an increased percentage of denatured lysozyme being deposited, compared with non silicone–containing materials. This study sought to investigate the impact of using a rewetting drop (Clerz® Plus Lens Drops; Alcon Laboratories) on the comfort and protein deposition that occurs when using a SH contact lens. Methods:A prospective, investigator–masked, randomized, cross–over clinical trial was conducted with 32 subjects. Each subject wore Focus Night&Day (FND) SH lenses on a 30–day continuous wear (CW) basis for one month, while inserting either 0.9% unpreserved unit–dose saline (S) or multi–dose Clerz Plus (CP) four–times per day. At the end of the month lenses were collected and replaced with a second pair, which were used with the second rewetting drop. All lenses were aseptically collected and immediately placed in 1.5 mL of extraction buffer, comprised of 50:50 acetonitrile:0.2% trifluoroacetic acid. Total protein was assessed using an Amido–black based dot–blot assay, lysozyme was quantified via Western blotting and the percentage of denatured lysozyme was determined using a modified Micrococcus lysodekticus assay. Results:While lens comfort was always greater and lens dryness always less with the CP drops, this difference was not significant (p=NS). Symptoms of dryness and comfort varied across the day regardless of drop–type (p<0.001), with dryness being maximal on waking, least in the middle of the day and increased towards the evening. CP drops provided greater comfort on insertion (p=0.02), better visual quality (p<0.01) and less mucous discharge on waking (p=0.015) than the control product. Total protein deposition was lower with the CP drops (1.7 vs 1.1 µg; p<0.001), as was lysozyme deposition (1.0 vs 0.7; p<0.001). The percentage of denatured lysozyme was also reduced when subjects used the CP drops compared with the control drops (85% vs 76%; p=0.002). Conclusions:The use of rewetting drops containing surface active agents may prove beneficial in the management of patients using SH lenses on a CW basis. The use of Clerz Plus drops provided greater subjective satisfaction, reduced protein deposition and reduced denatured lysozyme than a rewetting drop containing saline alone.

Keywords: contact lens