What is Dry Eye?

Chronic dry eye affects millions of people in the United States. The pathophysiology of dry eye has become increasingly better understood in the past several years. The tear film consists of three layers: the mucin layer, the aqueous layer, and the lipid layer. A problem in any or all of these layers leads to instability of the tear film, which leads to dry eye. The mucin layer is produced by the conjunctival tissue and allows equal distribution of the tear film across the ocular surface. The aqueous layer has many components, including water, proteins, antibodies, and electrolytes. The lipid layer, produced by the meibomian glands along the eyelid margin, is the most superficial layer and stabilizes the tear film by preventing evaporation. If the tear film does not adequately coat the ocular surface, individuals can experience such symptoms as redness, foreign body or gritty sensation, tearing, and fluctuating vision.