Understanding and analyzing meibomian lipids--a review.
OBJECTIVE
This review is intended to bring to the informed reader the current state of knowledge about meibomian lipids and the art for analyzing them.


METHODS
At the forefront of any endeavor, there are controversies, and these, along with future directions in the field, are brought to the reader's attention.


RESULTS
Function and anatomy of meibomian glands are briefly covered, giving insight into possible mechanisms for secretory controls. Anatomically, some anomalies in meibomian gland distribution of different species, such as whales versus dolphins, are presented, and, for the first time, the structure of the meibomian glands in a selection of marsupials is presented. In attempting to make the literature more accessible, lipid structure and nomenclature are described, and these structures are related to their possible effects on the physicochemical properties of meibomian lipids. The advantages and disadvantages of various collection and storage techniques are described, as well as how gas chromatography and combined HPLC and mass spectrometry coupled with fragmentation are currently enabling us to determine the nature of the lipids in very small samples.


CONCLUSIONS
This review extends to discussing the lipids in tears (as opposed to meibomian gland lipids) and briefly highlights new thoughts about the interactions between proteins of the tear film and meibomian lipids. A model that includes proteins in the outer layer of the tear film is also presented. This model is currently being critically analyzed by the ocular community. It concludes briefly by highlighting possible further areas of research in this area.
Department of Ophthalmology and Graduate School of Biomedical Sciences, University of Texas Southwestern Medical Center, Dallas, Texas, USA.
Igor A
IA
Butovich
Thomas J
TJ
Millar
Bryan M
BM
Ham
D000818:Animals; D002851:Chromatography, High Pressure Liquid; D005143:Eyelids / Q000378:metabolism; D006801:Humans; D050356:Lipid Metabolism / Q000502:physiology*; D008055:Lipids / Q000032:analysis*; D013058:Mass Spectrometry; D008537:Meibomian Glands / Q000737:chemistry* / Q000378:metabolism*; D013048:Specimen Handling; D013666:Tears / Q000378:metabolism
D008055:Lipids