title: Comparison of noninvasive tear break-up time measurements from black and white background instruments.
abstract: OBJECTIVE
  To compare noninvasive tear break-up time (NITBUT) measured using a black background instrument (NITBUTb) and that measured using a white background instrument (NITBUTw).
  
  
  METHODS
  The NITBUTb and NITBUTw of the right eye of 58 asymptomatic subjects aged 16 to 23 years were measured by the same examiner on the same day and compared. NITBUT measurement was terminated at 45 s to minimize ocular discomfort and reflex tearing.
  
  
  RESULTS
  Three subjects had reflex tearing during the NITBUT measurement, and nine subjects had either NITBUTb or NITBUTw values > 45 s, so their data were excluded. For the 46 subjects with NITBUT < or = 45 s, no significant difference between NITBUTb and NITBUTw was found (Wilcoxon test p = 0.156). No statistically significant relationship was found between NITBUTb and NITBUTw (Spearman r = 0.217, p = 0.147). The agreement between NITBUTb and NITBUTw was poor, with a mean difference of 1.3 s and 95% limits of agreement of -20.0 to +22.6 s.
  
  
  CONCLUSIONS
  There was no significant difference in NITBUT made from instruments of different backgrounds if the procedures and endpoint criterion were the same. The poor agreement between NITBUTb and NITBUTw was due to the large variations in NITBUT rather than the difference in the background color of the instrument used. However, use of the black background instrument for subjects with dark irides is recommended, as it is relatively easier to see the grid image on the eye and > 50% of our subjects complained of discomfort from glare with the white background instrument.
authors.affiliation: Department of Optometry and Radiography, The Hong Kong Polytechnic University, Hong Kong, SAR, China. orpaulin@polyu.edu.hk
authors.forename: Pauline
authors.initials: P
authors.lastname: Cho
authors.forename: Kwai-Ying
authors.initials: KY
authors.lastname: Ho
authors.forename: Yeung-Chi
authors.initials: YC
authors.lastname: Huang
authors.forename: Hon-Yee
authors.initials: HY
authors.lastname: Chui
authors.forename: Man-Chui
authors.initials: MC
authors.lastname: Kwan
mesh_terms: D000328:Adult; D001767:Blinking / Q000502:physiology; D003315:Cornea / Q000378:metabolism; D003941:Diagnostic Techniques, Ophthalmological / Q000295:instrumentation*; D005260:Female; D006801:Humans; D008297:Male; D013666:Tears / Q000737:chemistry*; D013997:Time Factors