Eyelid disorders: the meibomian gland, blepharitis, and contact lenses.

PURPOSE: To present our results to date on the evaluation of the pathophysiology of chronic blepharitis and its relationship to the tear lipid layer, and to propose a structure to that layer. METHODS: Compilation of work to date. RESULTS: A classification system of chronic blepharitis has been developed that has use in diagnosis, planning therapy, and assessment of mechanisms. Abnormalities in meibum have been identified that provide insight into disease mechanisms and have led to the development of a proposed structure to the tear lipid layer. A defect in polar lipids explaining the frequently associated evaporative dry eye has been identified. Mechanisms accounting for the therapeutic benefit of minocycline have been elucidated. CONCLUSION: Chronic blepharitis has associated meibum abnormalities that explain defects in the tear lipid layer that may result in a frankly unstable tear film and that explain the frequently associated evaporative dry eye.