Dry eyes can occur when either you don't produce enough tears or when a gap in the protective tear film allows moisture to be lost.
Dry eye syndrome can affect anyone, but it becomes more common with increasing age. Dry eyes possibly effect as many as a third of older people. Women are affected much more often than men.
The causes include:
Ageing. You tend to make fewer tears as you get older. In particular, some women notice dry eyes developing after the menopause.
Medication. Some medicines sometimes have a side-effect of causing dry eyes, or make dry eyes worse. These include:
'Water' tablets (diuretics).
Some treatments for anxiety and other psychological problems.
Beta-blockers such as propranolol, atenolol.
Some treatments for acne, etc.
Illness. Some people develop dry eyes as a symptom of a more general disease. For example, dry eyes may occur with rheumatoid arthritis, systemic lupus erythematosus (SLE) and Sjögren's syndrome. In these situations you would normally have other symptoms in other parts of the body such as joint pains.
Increased evaporation of tears. This may be due to:
Low humidity - for example, from central heating or air conditioning.
Low blink rate, often combined with opening your eyes wider than normal. For example, spending a long time looking at a computer, TV or microscope. Also people with Parkinson's disease can blink less.
Wearing contact lenses.
Windy conditions when you are outside.
Not being able to cover the eyes completely when closing the eyelids. For example, due to eye problems that some people have related to thyroid disease. Also, some people sleep with their eyes partly open.
Damage to the outer part of the eyes, eyelids, etc, from disease, injury or surgery.
Skin rashes such as seborrhoeic dermatitis or rosacea.
Inflammation of the eyelids (blepharitis), which is often associated with dry eyes.
Unknown. Some younger people have no apparent cause. They simply produce less than the normal amount of tears.
What are the symptoms of dry eyes?
Both eyes are usually affected. The eyes may not actually feel dry. Symptoms include:
Irritation in the eyes. The eyes may feel gritty or burning. However, the eyes do not go red. If they do, another eye problem or a complication is usually present.
Slight blurring of vision from time to time. However, dry eyes do not affect the seeing part of the eye, and dry eyes do not usually cause permanent damage to vision.
Discomfort in your eyes when looking at bright lights.
If you wear contact lenses, you may find they become uncomfortable.
To learn more about Dry eyes, visit EyeSmart.org