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Margarita Calonge, Alberto López-Miguel, Marisa Tesón, Vicente Martin-Montanez, Amalia Enriquez-De-Salamanca, Michael E Stern, Maria-Jesus J. Gonzalez; Lacrimal Functional Unit Response of Dry Eye Patients to Desiccating Conditions. Invest. Ophthalmol. Vis. Sci. 2014;55(13):1972.
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To determine if mild desiccating conditions can induce acute exacerbations in the lacrimal functional unit (LFU) of dry eye (DE) patients and similarly aged asymptomatic subjects.
Prospective cross-sectional study including DE patients and normal subjects, exposed to a controlled desiccating environment consisting of low (5%) relative humidity for 2 h in a controlled environmental research laboratory (CERLab). The following diagnostic tests were performed before and after exposure: tear osmolarity, phenol red thread test (PRTT), conjunctival hyperemia, fluorescein tear-break-up time, ocular surface vital staining, and Schirmer test. Additionally, 16 molecules in tear samples were analyzed by multiplex bead analysis.
Fifteen patients (age: 58.5±2.7 years) and 19 healthy subjects (age: 60.6±1.7 years) were included. Before exposure there were significant differences between patients and controls in all clinical tests except tear osmolarity and conjunctival hyperemia; tear EGF was decreased (p<0.001) in DE patients. After CERLab exposure, EGF was still lower in DE subjects and the following were significantly increased in DE patients: IL-1Ra (p=0.003), IL-6 (p=0.002), IL-8 (p=0.05), and MMP-9 (p=0.01). After 2-hr exposure to low humidity, DE patients and controls had a significant (p≤0.05) increase in tear osmolarity (from 317.3±3.3 to 332.5±6.8 and from 309.4±4.2 to 322.6±4.2 mOsmol/L, respectively), and corneal staining (from 2.60±0.30 to 3.27±0.27 and from 0.37±0.19 to 1.11±0.23, respectively). Controls had decreased (P<0.01) PRTT values, whereas DE patients had more conjunctival hyperemia (p≤0.05) after exposure. There were no significant changes in tear molecule concentrations in normals. In contrast, two tear molecules: IL-6 (from 96.6±37.8 to 185.4 ± 78.9 pg/ml; p≤0.01) and IL-1Ra (from 18040.0±4049.6 to 31935.6±5508.1 pg/ml; p=0.004) increased in DE patients.
Both asymptomatic controls and DE patients showed acute worsening after 2 hr of exposure to a desiccating environment, demonstrated by increased tear osmolarity and corneal staining. However, only DE patients had acute changes in their levels of some tear molecules. The reaction of the LFU to a mild desiccating environment may be useful in differentiating DE patients from normal controls.
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