Tiny glands in the eyelids (meibomian glands) make a small amount of lipid (fatty) liquid which covers the outer layer of the tear film. Cells at the front of the eye and inner part of the eyelids also make a small amount of liquid which adds to the tear film.
The tears then drain down small channels (canaliculi) on the inner side of the eye into a tear 'sac'. From here they flow down a channel called the tear duct (also called the naso-lacrimal duct) into the nose.
What are the causes of dry eyes?
Anything that reduces the normal amount of tears that you make may result in dry eyes. The causes include:
- Ageing. You tend to make less tears as you get older. In particular, some women notice dry eyes developing after the menopause.
- Medication. Some medicines which you may take for other conditions 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 medicine is causing your dry eyes. - Illness. 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.
- 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 for the reduced amount of tears and dry eyes.
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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 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 cause permanent damage to vision.
- You may not like bright lights.
- If you wear contact lenses, you may find they become uncomfortable.
Symptoms tend to be made worse by: windy weather which drys out the eyes further; tobacco smoke; low humidity; air-conditioning; when you blink less often, for example, when you read, or look at a computer screen or TV for long periods.
What is the treatment for dry eyes?
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Artificial tears
These come as eye drops, and are usually good at relieving symptoms. You can buy them at pharmacies or get them on prescription. At first, you may need to use them every hour or more to improve symptoms. Once symptoms improve, you may then only need to use them three or four times a day. You need to use them regularly to keep symptoms away.
There are several types of artificial tears with different ingredients. Occassionally, some people find one type may irritate. A change to a different preparation may help if the first does not suit.
Note: some types of artificial tears contain preservatives such as benzalkonium hexachloride. If you use drops that contain benzalkonium hexachloride for long periods, they may damage the front of the eye (the cornea). Therefore, if you use artificial tears more than four times per day long-term, it is best to use a 'preservative-free' brand which does not contain benzalkonium chloride.
Eye ointment
It may also help to use a soothing and lubricating ointment at bedtime for overnight. You can buy this too at pharmacies, or get it on prescription. You should not use ointment during the day as it may make the artificial tear drops less effective, and can blur vision. (Also, do not use eye ointment if you use other eye drops for other conditions such as glaucoma. The other eye drops may not work so well on top of an ointment.)
Other treatments
Artificial tears and soothing ointments work well in most cases. Other treatments may be advised by a specialist in severe cases not helped by the above. For example: medicines to boost tear production by the tear gland, or surgery to block the tears from draining away.
Contact lens wearers
You should not wear contact lenses whilst using many types of eye drops. Check with your doctor or pharmacist. It is often the preservative in the drops that may cause problems. Some types of drops are available without preservative which are suitable for contact lens wearers.
You should not wear contact lenses whilst using eye ointment.
©EMIS and PIP 2005 Updated: February 2005 Review Date: July 2006 CHIQ Accredited PRODIGY Validated
