title: Repeatability of a new method for measuring tear evaporation rates.
abstract: OBJECTIVE
  The purpose of this study was to evaluate the repeatability of tear evaporimetry based on infrared thermography in a clinical room setting and to test the effect of changing environmental humidity on ocular surface temperature (OST) and tear evaporation rates (TERs) in a controlled adverse environmental (CAE) chamber.
  
  
  METHODS
  Twenty-six healthy participants were enrolled, of whom 16 underwent repeatability measurements in a clinical room and 10 were exposed to a constant temperature of 30°C with a humidity of 45 and 65% in a CAE. Participants were acclimatized to each condition for at least 20 minutes before OSTs were taken. Tear film breakup time was assessed in the CAE only. Number of blinks and OSTs were continuously measured for 20 seconds for the cornea, conjunctiva, and overall ocular surface with an infrared camera; corresponding TERs were calculated.
  
  
  RESULTS
  The OSTs and TERs showed acceptable strength of agreement between the first and second measurements. The coefficients of repeatability were 0.4°C for OST and 6.0 W m for TER. An increase in chamber humidity (from 45 to 65%) increased OST (p < 0.05). The TER was not changed significantly (p > 0.05). The tear film breakup time and number of blinks were not significantly affected by different humidity conditions.
  
  
  CONCLUSIONS
  This technique has acceptable repeatability and has potential to document individual tear evaporation changes with time where humidity may differ by less than 20%.
authors: Singapore Eye Research Institute, 111 Third Hospital Ave., Singapore, Singapore.
authors: Andrea
authors: A
authors: Petznick
authors: Jen Hong
authors: JH
authors: Tan
authors: Shiao Khee
authors: SK
authors: Boo
authors: Sze Yee
authors: SY
authors: Lee
authors: U Rajendra
authors: UR
authors: Acharya
authors: Louis
authors: L
authors: Tong
mesh_terms: D000293:Adolescent; D000328:Adult; D001767:Blinking; D003315:Cornea / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D011446:Prospective Studies; D013666:Tears / Q000737:chemistry*; D055548:Vapor Pressure; D055815:Young Adult