[Measurement of tear evaporation from ocular surface]

A new method for measuring tear evaporation from the ocular surface is developed. The change of humidity in the closed chamber around the eye was recorded, with eyes open and eyes closed. Theoretical equations were used for data analysis, and the evaporation coefficient K, the tear evaporation volume at the environmental humidity of 40% were calculated. We examined 28 normal eyes and 58 eyes of dry eye patients. Evaporation coefficient K (x 10(-4)/sec) were 32.4 +/- 9.2 in normal and 16.5 +/- 11.3 in dry eyes (p less than 0.001). Tear evaporation volume at the environmental humidity of 40% (x 10(-7) g/sec.eye) were 16.2 +/- 4.7 in normal and 8.4 +/- 5.7 in dry eyes (p less than 0.001). This method is so simple and non-invasive that it could be used as a new examination for dry eye.