title: Tear breakup dynamics: a technique for quantifying tear film instability.
abstract: OBJECTIVE
  The purpose of this study was to develop a novel, quantitative measurement of tear film breakup dynamics (TBUD) to study the phenomenon of tear breakup in dry eye and control subjects and its impact on dry eye symptoms.
  
  
  METHODS
  Ten control and 10 dry eye subjects completed the Dry Eye (DEQ) and other questionnaires. After the instillation of sodium fluorescein, subjects kept the tested eye open for as long as possible, similar to a staring contest, while tear film breakup was videotaped (S-TBUD). The maximum blink interval (MBI) and tear breakup time (TBUT) were measured from digital movies by a masked observer. Individual frames of movies were converted to gray-scale images, maps of relative tear film fluorescence were generated, and the total area of tear breakup (AB) of the exposed cornea was quantified.
  
  
  RESULTS
  On average, dry eye subjects demonstrated a higher AB and shorter TBUT and MBI, but only the AB was significantly different (p = 0.023). Subjects most often used the descriptors stinging and burning to describe their sensations during staring trials. The AB showed a high correlation between eyes and with some DEQ symptom measures.
  
  
  CONCLUSIONS
  These methods allow objective quantification and tracking of the phenomenon of tear breakup. Our results suggest that tear breakup stresses the corneal surface, resulting in stimulation of underlying nociceptors. The tear film of dry eye subjects was less stable than controls. They had a larger AB measured from the last video frame before MBI (i.e., just before blinking) than did controls. This perhaps reflects adaptation to the repeated stress of tear instability in dry eye.
authors.affiliation: Indiana University School of Optometry, 800 E. Atwater Street, Bloomington, IN 47405, USA. cbegley@indiana.edu
authors.forename: Carolyn G
authors.initials: CG
authors.lastname: Begley
authors.forename: Nikole
authors.initials: N
authors.lastname: Himebaugh
authors.forename: Debra
authors.initials: D
authors.lastname: Renner
authors.forename: Haixia
authors.initials: H
authors.lastname: Liu
authors.forename: Robin
authors.initials: R
authors.lastname: Chalmers
authors.forename: Trefford
authors.initials: T
authors.lastname: Simpson
authors.forename: Jalaiah
authors.initials: J
authors.lastname: Varikooty
mesh_terms: D000328:Adult; D001767:Blinking / Q000502:physiology; D003287:Contrast Media / Q000008:administration & dosage; D003315:Cornea / Q000378:metabolism; D015352:Dry Eye Syndromes / Q000378:metabolism* / Q000503:physiopathology; D005260:Female; D019793:Fluorescein / Q000008:administration & dosage; D006801:Humans; D008297:Male; D008875:Middle Aged; D009883:Ophthalmic Solutions; D011795:Surveys and Questionnaires; D013666:Tears / Q000502:physiology*; D014741:Video Recording
chemical_list: D003287:Contrast Media; D009883:Ophthalmic Solutions; D019793:Fluorescein