title: Comparison of two artificial tear formulations  using aberrometry.
abstract: BACKGROUND
  This study investigates the effect of artificial tears of different viscosities on aberrations of healthy eyes.
  
  
  METHODS
  We recruited subjects from the student population of the Northeastern State University Oklahoma College of Optometry. Using the Complete Ophthalmic Analysis System (COAS), aberrometry measurements were taken every second for 60 seconds with a blink every 10 seconds. We made measurements of the naked eye, then after instillation of TheraTears non-preserved drops, and after instillation of SystanePF, a more viscous formulation. Zernike coefficients up to the sixth order were recorded and analysed. We evaluated changes in spherical and astigmatic dioptric powers and coma-like, spherical aberration-like and total higher-order aberration (HOA) RMS values as a function of time.
  
  
  RESULTS
  Both drops yielded significantly higher values than the naked eye for HOA RMS and cylindrical power as well as a hyperopic shift in spherical equivalent (p < 0.001,paired t-test). SystanePF, the more viscous tear, showed significantly higher values than TheraTears in HOA RMS and cylinder in all inter-blink periods (p < 0.001, paired t-test).
  
  
  CONCLUSIONS
  This study shows artificial tears can have a measurable and significant impact on aberrations of healthy eyes. This effect is sustained for at least one minute and its magnitude appears to be related to the viscosity of the tear formulation.
authors.affiliation: Northeastern State University, Oklahoma College of Optometry, 1001 N Grand Avenue, Tahlequah, OK 74464, USA.
authors.forename: Jeffrey S
authors.initials: JS
authors.lastname: Berger
authors.forename: Kyle R
authors.initials: KR
authors.lastname: Head
authors.forename: Thomas O
authors.initials: TO
authors.lastname: Salmon
mesh_terms: D000328:Adult; D016477:Artifacts; D001767:Blinking; D005260:Female; D006801:Humans; D008297:Male; D009883:Ophthalmic Solutions / Q000008:administration & dosage / Q000009:adverse effects* / Q000737:chemistry*; D009907:Optometry / Q000295:instrumentation / Q000379:methods*; D012029:Refraction, Ocular / Q000187:drug effects*; D012030:Refractive Errors / Q000139:chemically induced* / Q000175:diagnosis; D013666:Tears; D014783:Viscosity; D055815:Young Adult
chemical_list: D009883:Ophthalmic Solutions