title: High-speed videotopographic measurement of tear film build-up time.
abstract: OBJECTIVE
  To detect tear film regularity changes in the 15 seconds after a blink, by using a new high-speed videotopographic method.
  
  
  METHODS
  The new system, based on a standard corneal topograph, allows registration of four photokeratoscopic images per second. Altogether, 15 eyes of 15 healthy volunteers and 7 eyes of 7 patients with dry eye were examined in this prospective preliminary study. The main outcome measures were changes in surface regularity index (SRI), surface asymmetry index (SAI), and corneal power.
  
  
  RESULTS
  The corneal surface became more regular in the first few seconds after a blink. In healthy eyes, the trend line of SRI and SAI decreased (improved) significantly (P < 0.001) after a blink, in 10 of 15 eyes for the SRI and in 13 of 15 for the SAI. In the typical cases, the trend line for SRI reached its minimum level, on average, at 7.1 +/- 3.9 seconds after a blink and that for the SAI at 5.4 +/- 2.7 seconds. Similar trends were found in the dry-eye group. The changes in keratometric measures were small (mean range, <1.5% of the absolute value) and showed no definite trends.
  
  
  CONCLUSIONS
  High-speed videotopography provides the possibility of quantitative measurement of tear-film dynamics and may have clinical value in the management of ocular surface disorders. After a blink, it takes the tear film approximately 3 to 10 seconds (tear film build-up time) to reach the most regular state. However, despite surface-regularity changes, the measured corneal powers are stable.
authors.affiliation: First Department of Ophthalmology, Semmelweis University, Budapest, Hungary. nj@szem1.sote.hu
authors.forename: János
authors.initials: J
authors.lastname: Németh
authors.forename: Béla
authors.initials: B
authors.lastname: Erdélyi
authors.forename: Béla
authors.initials: B
authors.lastname: Csákány
authors.forename: Péter
authors.initials: P
authors.lastname: Gáspár
authors.forename: Alexandros
authors.initials: A
authors.lastname: Soumelidis
authors.forename: Ferenc
authors.initials: F
authors.lastname: Kahlesz
authors.forename: Zsolt
authors.initials: Z
authors.lastname: Lang
mesh_terms: D000328:Adult; D000368:Aged; D001767:Blinking; D003315:Cornea / Q000378:metabolism*; D019781:Corneal Topography; D015352:Dry Eye Syndromes / Q000378:metabolism*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009883:Ophthalmic Solutions / Q000008:administration & dosage; D011446:Prospective Studies; D013666:Tears / Q000378:metabolism*; D013997:Time Factors; D014743:Videotape Recording
chemical_list: D009883:Ophthalmic Solutions