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Background/Aims: Tissue degradation in corneal thinning disorders, such as keratoconus (KC), involves the expression of inflammatory mediators. The purpose of this study was to determine the levels of proinflammatory cytokines and matrix metalloproteinase 9 (MMP-9) in tears from both eyes of unilateral keratoconus (KC) patients.Methods: Thirty patients diagnosed with asymmetric KC (30 KC eyes, and 30 subclinical KC eyes) and 20 normal control subjects (1 eye) were studied in a prospective, cross sectional study.Keratoconus screening programs were performed on these participants. Ten microliters of tears were collected from each eye. The concentrations of cytokines (interleukin-6[IL-6] and tumor necrosis factor α [TNF-α]), and MMP-9 were measured by ELISA. Results:Mean values for IL-6 levels were similar in KC and subclinical KC samples .1] ng/mL) vs. subclinical KC eye (7.0 [4.8-8.6] ng/mL) (p<0.0001). MMP-9 levels in the control group (6.1 [3.9 -8.3] ng/mL) and subclinical KC were similar (p= 0.203).Conclusions: IL-6 and TNF-α are overexpressed in the tears of subclinical and KC eyes. Increased MMP-9 levels were found only in the KC eye. These results indicate that the pathogenesis of KC may involve chronic inflammatory events.

Purpose: To determine the concentration of interleukins (IL-1β and -6) and matrix metalloproteinase 9 (pro-MMP-9) in the tears of patients with different ocular surface diseases and to examine the possible relationship between the disorders and molecular inflammation. Methods: 77 patients diagnosed as having different ocular surface disorders and 18 normal control subjects were studied. Patients were routinely examined and separated into 5 groups: (1) control, (2) blepharitis, (3) ocular allergic disease, (4) dry eye and (5) conjunctivochalasis. Ten microliters of tears were collected by a Weck cell sponge. The concentrations of IL-1β, IL-6 and pro-MMP-9 were measured by enzyme-linked immunosorbent assay, and the MMP-9 activity was evaluated with gelatin zymography. Results: Levels of IL-1β and IL-6 in tear fluid were significantly higher in conjunctivochalasis (p = 0.0062 and p = 0.0134) than in the control group. Pro-MMP-9 levels were significantly elevated in blepharitis (p = 0.013), in allergic eye disease, in dry eye and in conjunctivochalasis (all p < 0.001), in comparison to controls. Conclusions: Pro-MMP-9 levels in tears are elevated in all of the studied pathologies especially in ocular allergy and conjunctivochalasis. However, IL-1β and IL-6 were only found to be overexpressed in conjunctivochalasis. These findings illustrate the selective implication of different molecules in each disorder.

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Wearing RGP CLs induces overexpression of IL-6, TNF-alpha, ICAM-1, and VCAM-1 in the tears of patients with keratoconus. These increased levels are higher in cases with severe keratoconus.