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M. LaFrance, R. Fullard; The Effects of Unilateral Punctal Occlusion on Tear Clearance and Tear Cytokines in Normal Human Subjects. Invest. Ophthalmol. Vis. Sci. 2008;49(13):427. doi: https://doi.org/.
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It has been proposed that punctal occlusion may alter tear cytokine concentrations based on the facts that: (1) tear clearance, a measure of the balance between tear production and elimination, declines following occlusion and (2) reduced tear clearance and increased levels of pro-inflammatory tear cytokines are correlated in dry eye patients. This study compares tear clearance values and the level of 24 tear cytokines following temporary unilateral punctal occlusion.
One randomly assigned eye of 23 normal subjects received superior and inferior unilateral intracanalicular punctal occlusion with six-month dissolvable HerrickTM plugs. Nonstimulated tear samples from both eyes were collected via micropipette (stored at -80 C) and tear clearance was measured using the Standardized Visual Scale Test (Macri 2000) prior to occlusion and again at 1, 4, and 7-weeks post occlusion. Tear cytokine concentrations were determined using a sandwich-ELISA based cytometric bead assay. Wilcoxon’s Matched Pairs test was used to compare contralateral tear clearance values at each interval and a generalized linear model with factors treatment and time was used to compare cytokine concentrations.
No between eye differences in tear clearance values were found prior to occlusion (p = 0.23). Following occlusion, reduced tear clearance was observed for the eye of occlusion at week 1 (p = 0.02), week 4 (p = 0.01), and week 7 (p < 0.0001). No statistically significant differences were observed between occluded or control eyes, nor was there a statistically significant interaction with time for the tear cytokines assayed: IL-1ra, IL-1β, IL-2, IL-4, IL-5, IL-6, IL-7, IL-8, IL-9, IL-10, IL-12p70, IL-13, IL-17, G-CSF, GM-CSF, IFNγ, Eotaxin, IP-10, MCP-1, MIP-1α, MIP-1β, PDGF-ββ, RANTES, and VEGF.
Unilateral punctal occlusion reduces tear clearance when compared to the fellow non-occluded eye in normal subjects. However, this did not alter the concentration of tear cytokines compared to pre-occlusion levels or when compared to the fellow non-occluded eyes. Therefore, punctal occlusion per se does not appear to alter the immune status of the tear film.
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