Dry eye syndrome (also known as keratoconjunctivitis sicca) is a common cause of eye irritation due to the eye surface being inadequately lubricated. Although this condition can affect anyone it tends to occur more often with increasing age (up to 7% of people in their 50's, increasing to around 15% of 70yr olds). Women are affected more than men.
There are two main reasons for dry eyes:
- 1. Inadequate tear production
- This occurs when the lacrimal tear gland fails to make a normal amount of tears. The amount of baseline tears produced can be measured using a "Schirmers test". This involves placing a thin strip of filter paper in the outer corner of the eye and checking how wet it becomes over a period of 5 minutes.
- 2. Tear instability
- In this situation there is a normal amount of tears produced but the tear quality is poor. The tears evaporate away too quickly, leaving dry areas on the front surface of the eye. The quality of the tear film can be measured using a technique called the "tear break up time", a test performed using a green fluoroscein dye.
Causes of dry eyes include:
- Often there is no specific cause other than fewer tears are made with age, some women in particular may notice a tendency to dry eyes after the menopause.
- Some medications can cause or exacerbate dry eyes eg: diuretics (water tablets), antidepressants, antihistamines, oral contraceptive pill.
- Eyelid margin disease, especially posterior blepharitis, which often results in increased tear evaporation from an unstable tear film (see BLEPHARITIS).
- Rarer general diseases which can be associated with reduced tear production from a diseased lacrimal gland include rheumatoid arthritis, systemic lupus erythematosus (SLE) and Sjogrens syndrome.
Symptoms of dry eyes
Most commonly both eyes are affected, although one side may be worse than the other. Surprisingly the eyes may not actually feel dry but possible symptoms include:
- Irritation of the eye surface including burning and /or gritty feeling.
- Intermittent blurring of vision due to poor wetting of the corneal window at the front of the eye.
- Red eyes, especially later in the day.
- Sensitivity to bright lights (photophobia).
- Contact lens wearers may find that their lenses do not wet properly. This can lead to fluctuations in vision, reduced comfort and shorter wearing times.
Dry eye treatment options
Most people tend to have relatively mild dry eyes and just require artificial tears to supplement their inadequate tear film. There are many different types on the market including drops, gels and thicker ointments. Often people have to try different preparations to find the one which suites them best. The drops are usually required a few times a day, sometimes more often depending on the humidity. When drops are required more than four times a day it is desirable to use a "preservative free" product in order to reduce the potentially toxic effect of preservatives on the eye surface.
Patients who have a reduced tear production and who are requiring frequent drops throughout the day are often helped by the use of "punctal plugs". These are a reversible way of reducing the drainage of tears into the nose. The plugs are easily placed in either the upper or lower tear hole (punctum) under topical anaesthetic in the out-patients.
Rarely other treatment options may be tried, such as using medications to increase tear production, or surgery can be used to permanently limit tear drainage.