title: Influence of Meibomian Gland Expression Methods on Human Lipid Analysis Results.
abstract: OBJECTIVE
  To compare the lipid composition of human meibum across three different meibum expression techniques.
  
  
  METHODS
  Meibum was collected from five healthy non-contact lens wearers (aged 20-35 years) after cleaning the eyelid margin using three meibum expression methods: cotton buds (CB), meibomian gland evaluator (MGE) and meibomian gland forceps (MGF). Meibum was also collected using cotton buds without cleaning the eyelid margin (CBn). Lipids were analyzed by chip-based, nano-electrospray mass spectrometry (ESI-MS). Comparisons were made using linear mixed models.
  
  
  RESULTS
  Tandem MS enabled identification and quantification of over 200 lipid species across ten lipid classes. There were significant differences between collection techniques in the relative quantities of polar lipids obtained (P<.05). The MGE method returned smaller polar lipid quantities than the CB approaches. No significant differences were found between techniques for nonpolar lipids. No significant differences were found between cleaned and non-cleaned eyelids for polar or nonpolar lipids.
  
  
  CONCLUSIONS
  Meibum expression technique influences the relative amount of phospholipids in the resulting sample. The highest amounts of phospholipids were detected with the CB approaches and the lowest with the MGE technique. Cleaning the eyelid margin prior to expression was not found to affect the lipid composition of the sample. This may be a consequence of the more forceful expression resulting in cell membrane contamination or higher risk of tear lipid contamination as a result of reflex tearing.
authors.affiliation: Brien Holden Vision Institute, Sydney, NSW, Australia; School of Optometry and Vision Science, University of New South Wales, Sydney, NSW, Australia; Vision Cooperative Research Centre, Sydney, NSW, Australia. Electronic address: c.kunnen@brienholdenvision.org.
authors.forename: Carolina M E
authors.initials: CM
authors.lastname: Kunnen
authors.affiliation: Illawarra Health and Medical Research Institute and School of Medicine, University of Wollongong, Wollongong, NSW, Australia.
authors.forename: Simon H J
authors.initials: SH
authors.lastname: Brown
authors.affiliation: Brien Holden Vision Institute, Sydney, NSW, Australia; School of Optometry and Vision Science, University of New South Wales, Sydney, NSW, Australia; Vision Cooperative Research Centre, Sydney, NSW, Australia.
authors.forename: Percy
authors.initials: P
authors.lastname: Lazon de la Jara
authors.affiliation: Brien Holden Vision Institute, Sydney, NSW, Australia; School of Optometry and Vision Science, University of New South Wales, Sydney, NSW, Australia; Vision Cooperative Research Centre, Sydney, NSW, Australia.
authors.forename: Brien A
authors.initials: BA
authors.lastname: Holden
authors.affiliation: Central Analytical Research Facility, Queensland University of Technology, Brisbane, QLD, Australia.
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Blanksby
authors.affiliation: Illawarra Health and Medical Research Institute and School of Medicine, University of Wollongong, Wollongong, NSW, Australia.
authors.forename: Todd W
authors.initials: TW
authors.lastname: Mitchell
authors.affiliation: Brien Holden Vision Institute, Sydney, NSW, Australia; School of Optometry and Vision Science, University of New South Wales, Sydney, NSW, Australia; Vision Cooperative Research Centre, Sydney, NSW, Australia.
authors.forename: Eric B
authors.initials: EB
authors.lastname: Papas
mesh_terms: D000328:Adult; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D008055:Lipids / Q000032:analysis*; D008297:Male; D013058:Mass Spectrometry; D008537:Meibomian Glands / Q000378:metabolism*; D013666:Tears / Q000737:chemistry*; D055815:Young Adult
chemical_list: D008055:Lipids
keywords: lipids; mass spectrometry; meibomian gland; meibum; meibum expression; phospholipids