There is now an increased recognition by clinicians that dry eye disease (DED) is a common disorder characterised by dryness and damage of the ocular surface. It affects quality of life, including aspects of physical, social and psychological functioning, because it induces ocular discomfort, burning sensation, light sensitivity, visual disturbances or even corneal erosions and infections. DED is also known as keratoconjunctivitis sicca, dry eye syndrome and dysfunctional tear syndrome.
DED prevalence has been reported to range from 5 % to 30 %, this being a likely result from differing study populations and DED definitions. In a large population study, Moss et al. reported the prevalence of dry eye to be 14.4 % in 3,722 subjects aged 48 to 91 years and noted that the prevalence of the condition doubled after the age of 59. As a consequence, DED prevalence is expected to increase in ageing populations, which will eventually make this health problem more prominent.1–4
In order to address the problem, the International Dry Eye Workshop (DEWS) defines dry eye as a multifactorial disease of the tears and ocular surface that results in symptoms of discomfort, visual disturbance and tear film instability with potential damage to the ocular surface. It is accompanied by increased osmolarity of the tear film and inflammation of the ocular surface.3–5
Indeed, DEWS has recognised dry eye as a disturbance of the lacrimal functional unit, an integrated system comprising the lacrimal glands, ocular surface (cornea, conjunctiva and meibomian glands) and lids, and the sensory and motor nerves that innervate them.3,4 Dysfunction of any component of the lacrimal functional unit may lead to ocular surface disease, related to inflammation and increased tear film osmolarity.
This multifactorial aetiopathogenesis explains why the clinical diagnosis of dry eye remains a challenge, not only due to the wide spectrum of alterations of the ocular surface with different aetiology and pathophysiology,5 but also due to the lack of well standardised diagnostic tests,6 and the fact that corneal surface is sensitive to external stimuli and, while the most diagnostic tests are overly invasive, the non-invasive tests are still considered expensive for everyday practice. Therefore, a holistic approach and a careful examination of tear film, cornea, eyelids, anatomically and functionally, as well as a thorough clinical history is needed to diagnose DED.3,5–8
Early diagnosis of DED and identification of the underlying cause is essential not only for the management of the ocular surface disease, but also for the diagnosis and management of the systematic disease,which might be occult, and may serve as a common link between ophthalmologists and physicians.9,10