Introduction: The meibum is a lipid rich secretion that is the primary component of the external layer of the two-layered corneal tear film. The meibomian glands produce the meibum, and meibomian gland dysfunction leads to the degradation of the tear film. This dysfunction is known to lead to ocular irritation, inflammation, and pathology. Understanding this relationship is critical to preventing ocular disease.
Methods: An extensive search of peer-reviewed literature focusing on the collection, quantification, and analysis of normal and abnormal meibum and tear lipids was performed by searching PubMed.
Results: Numerous collection and quantification techniques are described and their advantages and disadvantages are listed. Studies demonstrate that the meibum consists of a large array of polar (phospholipids, sphingolipids, and ω-hydroxy fatty acids) and non-polar (wax esters, cholesterol esters, diesters, free sterols, monoglycerides, diglycerides, triglycerides, free fatty acids, fatty acid amides, and hydrocarbons) lipids, and changes to these lipids are linked to ocular disease. Individual lipids correlated to pathology are described when possible. Lipid deposition patterns on silicone hydrogel contact lenses are also analyzed.
Conclusion: Research shows that the normal meibum and tear lipids are essential for normal ocular health. There is still a dearth of information about each lipid’s structure and quantity present due to the inherent difficulties of working with small sample sizes. Additional work needs to be performed to resolve these unanswered questions, so better treatments for blepharitis and dry eye syndrome can be devised and better contact lens materials can be engineered.