title: Comparison of tear film surface quality measured in vivo on water gradient silicone hydrogel and hydrogel contact lenses.
abstract: OBJECTIVE
  Recently, a new water gradient silicone hydrogel material has been introduced for a daily disposable lens. The aim of this study was to assess, in vivo, the prelens tear film surface quality (TFSQ) of this new lens in comparison with that of another daily disposable lens from the same manufacturer.
  
  
  METHODS
  Eleven subjects wore two pairs of hydrogel nelfilcon A and silicone hydrogel delefilcon A lenses in two nonconsecutive days. The noninvasive lateral shearing interferometry was used to analyze the prelens tear film and distinguish between different contact lens materials. Measurements were taken in natural blinking conditions after 6 hours of wear. Additionally, the subjective comfort was evaluated.
  
  
  RESULTS
  The presence of both lenses resulted in a TFSQ reduction as compared with the bare eye condition. Statistically significant (Wilcoxon rank sum test, P<0.012) smaller change in TFSQ was introduced by the water gradient material than the high water content material. A statistically significant correlation between the TFSQ results of the two lenses was found (Pearson correlation coefficient R=0.8, P<0.003), indicating high linearity of the measurement methodology with respect to the tested lens material. The correlation of subjective comfort in lenses was lower and found to be insignificant (R=0.6, P>0.05).
  
  
  CONCLUSIONS
  Although the prelens TFSQ is not always directly proportional to the lens water content, the results of the in vivo study showed that the new water gradient silicone hydrogel material impact less TFSQ as compared with its predecessor.
authors: Institute of Physics, Wroclaw University of Technology, Wroclaw, Poland.
authors: Dorota H
authors: DH
authors: Szczesna-Iskander
mesh_terms: D000328:Adult; D001767:Blinking / Q000502:physiology; D003263:Contact Lenses, Hydrophilic / Q000009:adverse effects; D004209:Disposable Equipment; D005260:Female; D006801:Humans; D020100:Hydrogels / Q000009:adverse effects / Q000737:chemistry*; D007368:Interferometry / Q000379:methods; D008297:Male; D012044:Regression Analysis; D012826:Silicone Elastomers / Q000009:adverse effects / Q000737:chemistry*; D013499:Surface Properties; D013666:Tears / Q000502:physiology*; D014867:Water / Q000737:chemistry*; D055815:Young Adult
chemical_list: D020100:Hydrogels; D012826:Silicone Elastomers; D014867:Water