Abstract
Purpose: :
Duration of contact lens wear and contact lens-associated disease induce changes in tear cytokine levels (Thakur and Wilcox, Exp Eye Res 1998, 2000). The current study compares the inflammatory response to 30 days of continuous versus daily contact lens wear through variations in the levels of 27 tear cytokines.
Methods: :
Adapted contact lens wearers were prescribed balafilcon A silicone hydrogel lenses. Entry criteria included absence of ocular surface and systemic disease, and normal tear prism height, non-invasive break-up time, fluorescein and lissamine green staining scores (n = 17). After a 2 week washout, one eye was randomly assigned to 30 days of continuous wear and the contralateral eye to daily wear. 5.5 µl non-stimulated tear samples were collected by polished micropipette on Day 0 immediately prior to lens insertion, and on days 3, 14 and 30 of lens wear. Tear levels of 27 cytokines were measured by cytometric bead-based assay (CBA). Differences in tear cytokine profiles as a function of treatment (continuous or daily wear) and time (study day) were assessed by ANOVA.
Results: :
Several key cytokines showed trends based on treatment effect. IL-6 remained relatively unchanged at Day 3, was significantly elevated in the continuous wear eye at Day 14 (Tukey’s hsd test, p<0.05), but not at Day 30. Other overall trends were apparent but paired data points did not reach significance. IL-12p70, IL-7 and IL-8 all increased in the continuous wear eye relative to daily wear at Days 3, 14 and 30. IL-1ra and VEGF levels increased in both eyes relative to Day 0; in particular at Days 14 and 30. IL-1 beta levels were lower in the treated eye at Days 3, 14 and 30. No clear trends were evident for IL-2, IL-5, IL-10, IFN-gamma or TNF-alpha.
Conclusions: :
Balafilcon A lenses are approved for 30 days of continuous wear, so a marked inflammatory response was not expected in either eye in this study. However, results suggest that continuous contact lens wear does present a more pro-inflammatory ocular surface environment than daily wear based in particular on trends in IL-6, IL-8 and IL-12p70. Trends for several other cytokines further indicate that, with minimal CBA design enhancement, this approach could be used as a predictive modeling tool for early detection of contraindications to extended lens wear. Tear CBA should also be useful to assess conditions such as dry eye, in which a more severe inflammatory response would be expected.
Keywords: contact lens • lacrimal gland • cytokines/chemokines