Dry eye syndrome is an abnormality of the tear film. Patients with dry eye experience eye discomfort and/or visual symptoms and it may lead to eye surface disorders. Dry eye syndrome is fairly common in adults over age 40.
The most common symptoms are the sensation of sand (or other foreign body) in the eye, reddening, irritation, pain, burning and photophobia.
Dry eye syndromes cover all disorders of the tear film. Tears are the thin liquid film that is continuously renewed and that protects the exposed ocular surface of the eye. Tears are produced by the main and accessory lacrimal glands and are excreted through the tear duct into the oropharynx. The tear film is made up of three layers:
Tear secretion includes basal and reflex secretion. The innervation of the main lacrimal gland is parasympathetic in nature; the peripheral afferents are mediated by the ophthalmic branch of the trigeminal nerve.
The main functions of the tear film are metabolic, lubricant and dioptric. For a well-being sensation, the lacrimal system must be in perfect condition: any change will cause varying degrees of ocular discomfort. The tear film can be altered by intrinsic or extrinsic (environmental) factors. These factors impact in various ways on the stability of the tear film, causing ocular discomfort which leads to symptoms such as burning, the sensation of a foreign body and lacrimation. This is a ‘vicious’ cycle of inflammation.
The main causes of dry eye syndrome include:
Some drugs such as beta-blockers, antihistamines and antidepressants or diseases such as diabetes, can reduce lacrimation.
A physical eye examination will detect changes in the conjunctiva and the tear film. In addition, tests can be performed:
The treatment of this condition is based on lubricant eye drops. In addition, it is fundamental to treat any underlying conditions (eye-related or not), to review systemic drug treatments which may cause eye dryness, and to make any necessary lifestyle changes, particularly related to diet and smoking.
Finally, it is useful to advise patients on how to reduce eye strain, such as blinking frequently, changing focus from near vision to distance vision, taking regular short breaks, checking ambient light, eliminating sources of reflected glare and regulating humidity and ventilation.
Report of the International Dry Eye Workshop (DEWS) 2007. The Ocular Surface 2007;5(2)