The correlation between the tear film lipid layer and dry eye disease

Dry eye, also known as keratoconjunctivitis sicca, can be due either to insufficient tear production or excessive tear evaporation, both resulting in tear hyperosmolarity that leads to symptoms of discomfort and ocular damage. Additionally, the severity of dry eye symptoms appears to be correlated to lipid layer thickness. It is now generally recognized that increased evaporation due to a compromised lipid layer is one of the most common etiologies for hyperosmolarity of the tear film. Thus, therapies targeted at replenishing or stabilizing the lipid layer are key to the treatment of dry eye, either as monotherapy or in conjunction with therapies designed to enhance aqueous production.