Utility of a Controlled Environment in the Diagnosis of Dry Eye Disease

Abstract

Purpose: : To evaluate the variation in diagnostic test and tear inflammatory molecule values in healthy and in mild-to-moderate dry eye disease (mDED) subjects after exposure to controlled environment conditions in an environmental chamber.

Methods: : A total of 74 subjects were recruited. 19 controls and 15 mDED patients were evaluated under "standard conditions" (45% relative humidity [RH], 930 mb of barometric pressure). 20 controls and 20 mDED patients were exposed to "adverse conditions" (5% RH, 750 mb, similar to aircraft cabin pressure, and localized air flow). A diagnostic test protocol, including inmmunobead-based analysis (Luminex) of 15 inflammatory molecules in tears, was performed before and after 2 hr of exposure. Results were expressed as mean±SEM.U-Mann Whitney and Kruskal Wallis tests were used for comparisons of independent sample groups. To compare the two moments of study, before and after exposure, Wilcoxon signed rank and McNemar tests were used for quantitative variables and for qualitative ones, respectively. Two-sided P-values ≤ 0.05 were considered statistically significant.

Results: : 1) "Standard conditions" provoked a significant increase in global (0-4, Oxford scale) corneal staining (0.53±0.16 to 1.11±0.24), nasal and inferior (0-4, Baylor scale) corneal staining (0.63±0.25 to 1.16±0.25 and 1.21±0.28 to 2.05±0.33, respectively), and conjunctival hyperemia (0.89±0.09 to 1.47±0.12); mDED patients developed a significant increase in central corneal staining (Baylor scale) (0.20±0.14 to 0.67±0.23) and conjunctival hyperemia (0.93±0.14 to 1.33±0.13). 2) "Adverse conditions" in healthy subjects elicited a significant increase in global corneal staining (0.70±0.15 to 1.70±0.18) and conjunctival hyperemia (1.28±0.13 to 1.58±0.12), and a significant decrease in T-BUT (3.53±0.43 to 2.08±0.26). Also, RANTES and IL-6 tear values increased and EGF tear values decreased, slightly but significantly. mDED patients had a significant increase in global corneal staining (0.50±0.14 to 1.25±0.19), corneal staining in all 5 areas (Baylor scale), and conjunctival hyperemia (1.10±0.11 to 1.43±0.11), whereas phenol red test (20.95±1.53 to 16.75±1.34) and T-BUT (2.18±0.28 to 1.53±0.20) decreased significantly; additionally, tear EGF levels decreased (p=0.03) and a two-fold increase in tear MMP-9 (p=0.005) was observed.

Conclusions: : Controlled environmental conditions can worsen ocular surface signs not only in mDED patients, but also in healthy subjects. Interestingly, some key inflammatory molecules showed significant variations, suggesting that an environmental chamber can be an interesting facility to look for potential biomarkers of disease and to establish a more reliable setting for clinical trials.

Keywords: cornea: tears/tear film/dry eye • inflammation • clinical (human) or epidemiologic studies: systems/equipment/techniques