Dry eye syndrome ('dry eyes') is a common cause of eye irritation. It mainly affects older people. Artificial tears, gels and soothing ointments usually ease symptoms.

Dry eye syndrome also known as keratoconjunctivitis sicca occurs when there is a problem with the tear film that normally keeps the eye moist and lubricated. It can occur as a result of various conditions.
What is the tear film? The tear film is actually made up from three layers - the main middle watery layer, the thin outer oily layer, and the thin inner mucus layer.


The main middle watery layer is what we may think of as 'tears'. The watery fluid comes from the lacrimal glands. There is a lacrimal gland just above, and to the outer side, of each eye. The lacrimal glands constantly make a small amount of watery fluid which drains onto the upper part of the eyes. When you blink the eyelid spreads the tears over the front of the eye.

Tiny glands in the eyelids make a small amount of oily liquid which covers the outer layer of the tear film. This layer helps to keep the tear surface smooth and to reduce evaporation of the watery tears.

Cells of the conjunctiva at the front of the eye and inner part of the eyelids also make a small amount of mucus-like fluid. This allows the watery tears to spread evenly over the surface of the eye.

The tears then drain down small channels on the inner side of the eye into a tear 'sac'. From here they flow down a channel called the tear duct into the nose.

Dry eyes can affect anyone, but it becomes more common with increasing age. Dry eyes affects about 7 in 100 people in their 50s, and about 15 in 100 people in their 70s. Women are affected more often than men.

Another thing that can cause dry eyes is ageing. You tend to make less tears as you get older. In particular, some women notice dry eyes developing after the menopause.
Medication can also have an effect. Some drugs sometimes have a side-effect of causing dry eyes, or make dry eyes worse. These include: diuretics ('water tablets'); some antidepressants; antihistamines; some treatments for anxiety and other psychological problems; the contraceptive pill; beta-blockers such as propranolol, atenolol, etc; some eye drops used to treat other eye conditions. This is not an exhaustive list. Tell you doctor if you suspect that a drug is causing your dry eyes.
Some people develop dry eyes as a symptom of a more general disease. For example, dry eyes may occur with rheumatoid arthritis, SLE (systemic lupus erythematosus), and Sjogren's syndrome. In these situations you would normally have other symptoms in other parts of the body. For example, joint pains.

There are other reasons as well why this condition might occur and some of them are;

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.
Windy conditions when you are outside.
Inability to completely cover the eyes 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.
Blepharitis (inflammation of the eyelids) is often associated with dry eyes.
Unknown. Some younger people have no apparent cause.They simply produce less than the normal amount of tears.

With dry eyes, both eyes are usually affected. The eyes may not actually feel 'dry' but the 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.
You may not like bright lights.
If you wear contact lenses, you may find they become uncomfortable.
What are the possible complications of dry eyes?
Complications are uncommon. Inflammation of the conjunctiva (conjunctivitis) or the cornea at the front of the eye (keratitis) sometimes occurs. In severe cases, small ulcers may develop on the cornea. Rarely, the corneal may perforate (puncture).

See a doctor if the eye goes red or if vision becomes affected (more than slight temporary blurring). Also if eye pain develops other than the grittiness or irritation that goes with dry eyes. These are not normally symptoms of dry eyes and may indicate another eye condition or a complication of dry eyes.