title: A new, specular reflection-based, precorneal tear film stability measurement technique in a rabbit model: viscoelastic increases tear film stability.
abstract: OBJECTIVE
  To develop a safe, noninvasive, noncontact, continuous in vivo method to measure the dehydration rate of the precorneal tear film and to compare the effectiveness of a viscoelastic agent in maintaining the precorneal tear film to that of a balanced salt solution.
  
  
  METHODS
  Software was designed to analyze the corneal reflection produced by the operating microscope's coaxial illumination. The software characterized the shape of the reflection, which became distorted as the precorneal tear film evaporated; characterization was accomplished by fitting an ellipse to the reflection and measuring its projected surface area. Balanced salt solution Plus (BSS+) and a 2% hydroxypropylmethylcellulose viscoelastic were used as the test agents. The tear film evaporation rate was characterized and compared over a period of 20 minutes in 20 eyes from 10 New Zealand white rabbits.
  
  
  RESULTS
  The ellipse axes ratio and surface area were found to decrease initially after each application of either viscoelastic or BSS+ and then to increase linearly as the tear film began to evaporate (P < 0.001) for eyes treated with BSS+ only. Eyes treated with BSS+ required 7.5 ± 2.7 applications to maintain sufficient corneal hydration during the 20-minute test period, whereas eyes treated with viscoelastic required 1.4 ± 0.5 applications. The rates of evaporation differed significantly (P < 0.043) between viscoelastic and BSS+.
  
  
  CONCLUSIONS
  The shape and surface area of the corneal reflection are strongly correlated with the state of the tear film. Rabbits' corneas treated with viscoelastic remained hydrated significantly longer than corneas treated with BSS+.
authors.affiliation: Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, Florida, United States.
authors.forename: Derek
authors.initials: D
authors.lastname: Nankivil
authors.affiliation: Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, Florida, United States.
authors.forename: Alex
authors.initials: A
authors.lastname: Gonzalez
authors.affiliation: Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, Florida, United States.
authors.forename: Esdras
authors.initials: E
authors.lastname: Arrieta
authors.affiliation: Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, Florida, United States.
authors.forename: Cornelis
authors.initials: C
authors.lastname: Rowaan
authors.affiliation: Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, Florida, United States.
authors.forename: Mariela C
authors.initials: MC
authors.lastname: Aguilar
authors.affiliation: Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, Florida, United States.
authors.forename: Krystal
authors.initials: K
authors.lastname: Sotolongo
authors.affiliation: Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, Florida, United States Anne Bates Leach Eye Hospital, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, Florida, United States.
authors.forename: Florence A
authors.initials: FA
authors.lastname: Cabot
authors.affiliation: Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, Florida, United States Anne Bates Leach Eye Hospital, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, Florida, United States.
authors.forename: Sonia H
authors.initials: SH
authors.lastname: Yoo
authors.affiliation: Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, Florida, United States.
authors.forename: Jean-Marie A
authors.initials: JM
authors.lastname: Parel
mesh_terms: D000818:Animals; D001767:Blinking; D003315:Cornea / Q000502:physiology*; D003316:Corneal Diseases / Q000175:diagnosis* / Q000378:metabolism; D003681:Dehydration / Q000175:diagnosis* / Q000378:metabolism; D004195:Disease Models, Animal; D007368:Interferometry / Q000379:methods*; D011817:Rabbits; D013666:Tears / Q000737:chemistry*; D014783:Viscosity
keywords: balanced salt solution; corneal hydration; evaporation; precorneal tear film stability; viscoelastic