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Ranjini Kottaiyan, Gheorghe Salahura, James Zavislan, Geunyoung Yoon, James Aquavella, Ocular Surface Laboratory; Effects of Stressed Environments on the Ocular Surface Temperature, Lipid Layer Thickness and Heterogeneity. Invest. Ophthalmol. Vis. Sci. 2013;54(15):950.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate the effects of low relative humidity (RH) and high temperature conditions on the ocular surface temperature (OST), tear lipid thickness (LT) and uniformity in normal and dry eye subjects using thermal imaging and quantitative tearscope for imaging the lipid layer.
A total of 18 eyes comprising 5 normal, 9 aqueous deficiency (ADDE) and 4 with meibomian gland dysfunction (MGD) were included in the study. ADDE and MGD were diagnosed based on clinical criteria. Measurements were taken with a thermal camera and a quantitative tearscope before and after 30 minutes acclimation to three different environmental conditions in our controlled environmental chamber. The three conditions are 40% RH and 75 °F (condition 1), 20% RH and 75 °F (condition 2), and 40% RH and 85 °F (condition 3). Subjects were asked to blink once every 5 seconds for about 3-4 times during the measurements. Thermal data was analyzed to calculate the average OST in the central 9 mm of the cornea, while the average LT and uniformity were calculated from approximately the central one-third of the cornea, excluding the pupillary region. Changes in OST and LT were compared amongst the different groups.
The average OST is 34.9 ± 0.2°C, 33.8 ± 0.3°C and 34.6 ± 0.2°C in normal, ADDE and MGD subjects respectively. The average LT is 40.4 ±8.3 nm, 57.9 ± 30 nm, and 39.6±7.8 nm in normal, ADDE and MGD subjects respectively at baseline. After 30 min of acclimation, normal subjects did not show a significant change in OST under any of the conditions. ADDE, however, showed a significant increase in OST by 0.6°C, 0.4°C and 0.6°C in conditions 1 (p=0.01), 2 (p=0.02) and 3 (p=0.005) respectively. MGD showed an increasing trend in OST in conditions 1 and 2, but an interesting decreasing trend in condition 3 although none of these trends showed a statistical significance. On the lipid thickness, ADDE showed an increase in LT by 8.77 ± 10.95 nm and a decrease of 14.47 ± 29.04 nm, in conditions 1 and 2 respectively. Also, MGD showed an increase of heterogeneity by 0.18 ± 0.19 and a less relative heterogeneity of 0.14 ± 0.23 in conditions 2 and 3 respectively.
The dry eye groups differ in responding to different stressed environmental conditions.This finding suggests that the effects of the ocular stressors on the tear parameters can enhance our ability to differentiate the various dry eye symptoms.
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