Definition of dry eye syndrome
Dry eye syndrome is a multifactorial disease of the tears and ocular surface that results in a range of symptoms, including discomfort, visual disturbance, tear film instability and potential damage to the ocular surface. It is accompanied by increased osmolarity of the tear film and inflammation of the ocular surface. The Ocular Surface, 2007, pp.77. 2007 Report of the International Dry Eye Workshop (DEWS). [Online] Tear Film and Ocular Surface Society. Available at: www.tearfilm.org/dewsreport
Dry eye syndrome is a disturbance of the Lacrimal Functional Unit, which comprises the lacrimal glands, ocular surface (cornea, conjunctiva and meibomian glands) and eyelids, together with the sensory and motor nerves that link them.
The key features of dry eye syndrome are:
- Decreased tear production
- Increased tear evaporation
- Incorrect composition of tears
These result in inadequate lubrication of the eyes.
Dry eye is a catch-all term referring to abnormalities of the tear layer which normally coats the surfaces of the eyes, providing clear vision and protecting sensitive surface tissues. Other names for dry eye syndrome include chronic dry eye, dry eye disease and keratoconjunctivitis sicca.