title: Tear film dynamics on soft contact lenses.
abstract: OBJECTIVE
  To analyze and model the dynamics of tear film surface quality (TFSQ) in a group of subjects with healthy eyes, before and during contact lens (CL) wear, and in a group of subjects with dry eyes (DEs).
  
  
  METHODS
  Four sets of TFSQ measurements with lateral shearing interferometry were retrospectively analyzed on two groups of subjects. The first group included 13 CL wearers for which TFSQ measurements corresponding to baseline, Best CL, and Worst CL were selected. The second group included 13 DE subjects. The acquired TFSQ time series were fit with a power-exponential model. Tear film surface quality stability time, best TFSQ, and integrated poststability time characterizing the tear film deterioration process were derived.
  
  
  RESULTS
  The proposed power-exponential model was better suited (higher correlation values) for the TFSQ dynamics on CL rather than for those of baseline and DE measurements. The average baseline TFSQ Stability Time was significantly longer (p < 0.001) than those in the DE group and with both the best and worse CL. The average Best TFSQ achieved at baseline was statistically significantly better (p = 0.03) than that for the DE group. The average best TFSQ was significantly better (p < 0.01) for the Best CL than for that of the Worst CL. Deterioration of TFSQ on both best and Worst CL was substantially faster than that achieved for the DE group.
  
  
  CONCLUSIONS
  The observed distinct change in the sign of the TFSQ velocity on contact lenses suggests a two-phase dynamics in which the postblink stability phase is followed by a phase of dewetting. Lens material properties influence the first phase but play little role after the dewetting process occurs.
authors.affiliation: *PhD †PhD, DSc Institute of Physics, Wroclaw University of Technology, Wroclaw, Poland (DHS-I); and Institute of Biomedical Engineering and Instrumentation, Wroclaw University of Technology, Wroclaw, Poland (DRI).
authors.forename: Dorota H
authors.initials: DH
authors.lastname: Szczesna-Iskander
authors.forename: D Robert
authors.initials: DR
authors.lastname: Iskander
mesh_terms: D000328:Adult; D000368:Aged; D003263:Contact Lenses, Hydrophilic; D003315:Cornea / Q000503:physiopathology*; D015352:Dry Eye Syndromes / Q000503:physiopathology*; D005260:Female; D006801:Humans; D007368:Interferometry; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D013666:Tears / Q000502:physiology*; D055815:Young Adult