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E. Uchiyama, J.D. Aronowicz, I.A. Butovich, J.P. McCulley; Increased Evaporative Rates in Low Humidity Conditions Simulating Airplane Travel: A Probable Cause of Dry Eye Symptoms . Invest. Ophthalmol. Vis. Sci. 2006;47(13):248.
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© ARVO (1962-2015); The Authors (2016-present)
To quantitatively establish the relationship between low relative humidity (RH) conditions during flights and the increase in aqueous tear evaporation as an explanation for increased dry eye symptoms.
A prospective experimental laboratory study was conducted comparing changes in evaporative rates at RH conditions similar to those found in airplanes and those found at sea level. Twenty–nine subjects; 21 females and 8 males were evaluated; 18 with aqueous tear deficiency dry eye and 11 normals. Evaporative rate was calculated under two different ranges of increasing RH, from 20% to 25% (similar to Airplane RH), and from 40% to 45% (similar to sea level RH). The results were reported in µl of water evaporated per cm2 of exposed ocular surface per minute. Data from each eye of all study subjects were included in the analyses.
There was a 20% difference between the two humidity conditions compared in this study. The difference in corresponding evaporative rates at the two RH levels evaluated was statistically significant in all groups: dry eye patients, p ≤ 0.001; and normal subjects, p ≤ 0.001. As an average, the evaporative rate increased 99.72% (p ≤ 0.001) when the eyes where exposed to the lower humidity range similar to the found in airplanes as compared to higher RH range.
These studies show quantitatively the impact of low RH conditions similar to those present in airplanes, on the dynamics of the aqueous tear evaporation. They also document that RH affects the rate of aqueous tear evaporation in both normal subjects and dry eye patients. The recognized increase in clinical symptoms associated with low humidity present in airplanes can be attributed to an increase in aqueous tear evaporation. Prophylactic measures, such as the use of artificial tear drops, should be considered before and during exposure to these conditions in order to avoid the exacerbation of dry eye symptoms.
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