title: Evaporation and Hydrocarbon Chain Conformation of Surface Lipid Films.
abstract: The inhibition of the rate of evaporation (Revap) by surface lipids is relevant to reservoirs and dry eye. Our aim was to test the idea that lipid surface films inhibit Revap.
  
  
  
  Revapwere determined gravimetrically. Hydrocarbon chain conformation and structure were measured using a Raman microscope. Six 1-hydroxyl hydrocarbons (11-24 carbons in length) and human meibum were studied. Reflex tears were obtained from a 62-year-old male.
  
  
  
  The Raman scattering intensity of the lipid film deviated by about 7 % for hydroxyl lipids and varied by 21 % for meibum films across the entire film at a resolution of 5 μm2. All of the surface lipids were ordered. Revapof the shorter chain hydroxyl lipids were slightly (7%) but significantly lower compared with the longer chain hydroxyl lipids. Revapof both groups was essentially similar to that of buffer. A hydroxyl lipid film did not influence Revapover an estimated average thickness range of 0.69 to >6.9 μm. Revapof human tears and buffer with and without human meibum (34.4 μm thick) was not significantly different. Revapof human tears was not significantly different from buffer.
  
  
  
  Human meibum and hydroxyl lipids, regardless of their fluidity, chain length, or thickness did not inhibit Revapof buffer or tears even though they completely covered the surface. It is unlikely that hydroxyl lipids can be used to inhibit Revapof reservoirs. Our data do not support the widely accepted (yet unconfirmed) idea that the tear film lipid layer inhibits Revapof tears.
authors.affiliation: Department of Ophthalmology and Visual Sciences, University of Louisville School of Medicine, Louisville, KY 40202, USA.
authors.forename: Samiyyah M
authors.initials: SM
authors.lastname: Sledge
authors.affiliation: Department of Ophthalmology and Visual Sciences, University of Louisville School of Medicine, Louisville, KY 40202, USA.
authors.forename: Hussain
authors.initials: H
authors.lastname: Khimji
authors.affiliation: Department of Ophthalmology and Visual Sciences, University of Louisville School of Medicine, Louisville, KY 40202, USA. Electronic address: borchman@louisville.edu.
authors.forename: Douglas
authors.initials: D
authors.lastname: Borchman
authors.affiliation: Department of Ophthalmology and Visual Sciences, University of Louisville School of Medicine, Louisville, KY 40202, USA.
authors.forename: Alexandria L
authors.initials: AL
authors.lastname: Oliver
authors.affiliation: Department of Ophthalmology and Visual Sciences, University of Louisville School of Medicine, Louisville, KY 40202, USA.
authors.forename: Heidi
authors.initials: H
authors.lastname: Michael
authors.affiliation: Department of Ophthalmology and Visual Sciences, University of Louisville School of Medicine, Louisville, KY 40202, USA.
authors.forename: Emily K
authors.initials: EK
authors.lastname: Dennis
authors.affiliation: Department of Ophthalmology and Visual Sciences, University of Louisville School of Medicine, Louisville, KY 40202, USA.
authors.forename: Dylan
authors.initials: D
authors.lastname: Gerlach
authors.affiliation: Department of Ophthalmology and Visual Sciences, University of Louisville School of Medicine, Louisville, KY 40202, USA.
authors.forename: Rahul
authors.initials: R
authors.lastname: Bhola
authors.affiliation: Department of Ophthalmology and Visual Sciences, University of Louisville School of Medicine, Louisville, KY 40202, USA.
authors.forename: Elsa
authors.initials: E
authors.lastname: Stephen
mesh_terms: D000328:Adult; D002648:Child; D002675:Child, Preschool; D005136:Eye Proteins / Q000032:analysis*; D005260:Female; D006801:Humans; D006838:Hydrocarbons / Q000032:analysis*; D006878:Hydroxides; D008055:Lipids / Q000032:analysis*; D008297:Male; D008537:Meibomian Glands / Q000737:chemistry*; D008875:Middle Aged; D013059:Spectrum Analysis, Raman; D013499:Surface Properties; D013666:Tears / Q000737:chemistry*; D014835:Volatilization; D055815:Young Adult
chemical_list: D005136:Eye Proteins; D006838:Hydrocarbons; D006878:Hydroxides; D008055:Lipids; C042434:tear proteins; C031356:hydroxide ion
keywords: dry eye; hydroxyl lipids; meibum; tear evaporation; tear film lipid layer