title: Assessment of variation in bulbar conjunctival redness, temperature, and blood flow.
abstract: OBJECTIVE
  To assess the diurnal variation in bulbar conjunctival redness, conjunctival temperature, and conjunctival blood flow.
  
  
  METHODS
  Bulbar redness was quantified by CIE u' chromaticity using a SpectraScan PR650 spectrophotometer. Conjunctival temperature was measured using a Tasco-Thi 500 infrared thermometer. Measurements of conjunctival blood flow were obtained using a modified Heidelberg Retinal Flowmeter (HRF). Measurements on 10 subjects were made on a periodic basis over the day and on waking.
  
  
  RESULTS
  For each factor measured a cyclical pattern was observed, with highest values on waking, a reduction in values towards mid-day, and then a gradual increase over the remainder of the day. There was a significant effect of time for redness, temperature, and conjunctival blood flow (p < 0.001 for all three variables), with no significant difference in the cyclical pattern between eyes being observed (p = NS).
  
  
  CONCLUSIONS
  Diurnal bulbar redness, temperature, and conjunctival blood flow variation may be objectively quantified and all three are lowest during the middle of the day and maximal at the start of the day. This information should be considered when undertaking studies in which redness, temperature, and ocular surface blood flow are important outcome variables and time of day is a potential confounding factor.
authors.affiliation: Centre for Contact Lens Research, School of Optometry, University of Waterloo, 200 University Avenue, Waterloo, Ontario, Canada. svaccari@scimail.uwaterloo.ca
authors.forename: Stephanie
authors.initials: S
authors.lastname: Duench
authors.forename: Trefford
authors.initials: T
authors.lastname: Simpson
authors.forename: Lyndon W
authors.initials: LW
authors.lastname: Jones
authors.forename: John G
authors.initials: JG
authors.lastname: Flanagan
authors.forename: Desmond
authors.initials: D
authors.lastname: Fonn
mesh_terms: D000203:Activities of Daily Living; D000328:Adult; D001783:Blood Flow Velocity / Q000502:physiology*; D001831:Body Temperature / Q000502:physiology*; D002940:Circadian Rhythm / Q000502:physiology*; D003228:Conjunctiva / Q000098:blood supply*; D004867:Equipment Design; D005260:Female; D006801:Humans; D017078:Laser-Doppler Flowmetry / Q000295:instrumentation; D008297:Male; D012016:Reference Values; D015203:Reproducibility of Results; D013053:Spectrophotometry / Q000295:instrumentation; D013821:Thermometers