Dendritic immune cell densities in the central cornea associated with soft contact lens types and lens care solution types: a pilot study

BACKGROUND The purpose of this study was to assess whether differences in central corneal dendritic immune cell densities associated with combinations of soft contact lenses and lens care solutions could be detected by in vivo confocal microscopy. METHODS Participants were adults naïve to contact lens wear (n = 10) or who wore soft contact lenses habitually on a daily-wear schedule (n = 38) or on a study-assigned schedule for 30 days with daily disposable silicone hydrogel lenses (n = 15). Central corneas were scanned using an in vivo confocal microscope. Cell densities were compared among groups by demographic parameters, lens materials, and lens care solutions (polyhexamethylene biguanide [PHMB], polyquaternium-1 and myristamidopropyl dimethylamine [PQ/MAPD], peroxide, or blister pack solution [for daily disposable lenses]). RESULTS Among lens wearers, no associations were observed between immune cell densities and age, gender, or years of lens-wearing experience. Mean cell density was significantly lower (P < 0.01) in nonwearers (29 ± 23 cells/mm(2), n = 10) than in lens wearers (64 ± 71 cells/mm(2), n = 53). Mean cell density was lower (P = 0.21) with traditional polymer lenses (47 ± 44 cells/mm(2), n = 12) than with silicone hydrogel lenses (69 ± 77 cells/mm(2), n = 41). Lowest to highest mean density of immune cells among lens wearers was as follows: PQ/MAPD solution (49 ± 28 cells/mm(2)), blister pack solution (63 ± 81 cells/mm(2)), PHMB solution (66 ± 44 cells/mm(2)), and peroxide solution (85 ± 112 cells/mm(2)). CONCLUSION In this pilot study, in vivo confocal microscopy was useful for detecting an elevated immune response associated with soft contact lenses, and for identifying lens-related and solution-related immune responses that merit further research.