Human corneal epithelial cell shedding and fluorescein staining in response to silicone hydrogel lenses and contact lens disinfecting solutions.
A pilot study was conducted to evaluate human corneal epithelial cell shedding in response to wearing a silicone hydrogel contact lens/solution combination inducing corneal staining. The nature of ex vivo collected cells staining with fluorescein was also examined. A contralateral eye study was conducted in which up to eight participants were unilaterally exposed to a multipurpose contact lens solution/silicone hydrogel lens combination previously shown to induce corneal staining (renu® fresh™ and balafilcon A; test eye), with the other eye using a combination of balafilcon A soaked in a hydrogen peroxide care system (Clear Care®; control eye). Lenses were worn for 2, 4 or 6 hours. Corneal staining was graded after lens removal. The Ocular Surface Cell Collection Apparatus was used to collect cells from the cornea and the contact lens. In the test eye, maximum solution-induced corneal staining (SICS) was observed after 2 hours of lens wear (reducing significantly by 4 hours; p < 0.001). There were significantly more cells collected from the test eye after 4 hours of lens wear when compared to the control eye and the collection from the test eye after 2 hours (for both; n = 5; p < 0.001). The total cell yield at 4 hours was 813 ± 333 and 455 ± 218 for the test and control eyes, respectively (N = 5, triplicate, p = 0.003). A number of cells were observed to have taken up the fluorescein dye from the initial fluorescein instillation. Confocal microscopy of fluorescein-stained cells revealed that fluorescein was present throughout the cell cytoplasm and was retained in the cells for many hours after recovery from the corneal surface. This pilot study indicates that increased epithelial cell shedding was associated with a lens-solution combination which induces SICS. Our data provides insight into the transient nature of the SICS reaction and the nature of fluorescein staining observed in SICS.