Abstract
The term
dry eye refers to an ocular surface condition caused by a group of diseases sharing the common signs and symptoms of dryness. Dry eye syndrome (DES) and keratoconjunctivitis sicca (KCS) are often used interchangeably; however, they are actually separate conditions that lie along a disease spectrum that affects the wetting and lubricating properties of tears. KCS is a specific disorder causing dry eyes because of a qualitative and quantitative abnormality of lacrimal gland secretions. DES can result from decreased production of tears, increased evaporation of tears, or an abnormality in specific constituents of the tear film aqueous, oily, or mucin layer.
DES is made up of a constellation of clinical signs and symptoms that share a common theme of an altered and abnormal tear film. Patient complaints are vague, but include a number of similar symptoms, including foreign body sensation, dryness, burning, photophobia, blurry vision, easily fatigued eyes, and ocular pain.
The clinical symptoms in various disease processes are the same, but result from different pathology, including lacrimal gland dysfunction, meibomian gland abnormality, goblet cell dysfunction, or exposure. In all cases, however, there is an alteration in the tear film quantity, tonicity, or stability.