Dry eye syndrome (dry eyes) is a common cause of eye irritation, mainly affecting older people. Artificial tears, gels and soothing ointments usually ease symptoms.
Dry eye syndrome (also known as keratoconjunctivitis sicca, or simply dry eyes) 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.
This is made up from three layers - the main middle watery layer, the thin outer oily (lipid) 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. These glands make watery fluid which drains on to 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 (meibomian glands) make a small amount of lipid (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 (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 nasolacrimal duct) into the nose.
Dry eyes can affect anyone, but it becomes more common with increasing age. Dry eyes affect about 7 in 100 people in their 50s, and about 15 in 100 people in their 70s. Women are affected more often than men.
The causes include:
Both eyes are usually affected. The eyes may not actually feel dry. Symptoms include:
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.
A doctor can usually diagnose dry eyes from the symptoms. However, as dry eyes can be a symptom of an underlying disease (such as Sjögren's syndrome), don't be surprised if your doctor asks about all sorts of other symptoms.
Sometimes a test is done to confirm the diagnosis of dry eyes. This is called Schirmer's Tear Test. This measures the amount of tears that you form. Special filter paper is placed under the lower lid of your eye and left for five minutes. The amount of tears that you make can be assessed by how wet the filter paper becomes after five minutes.
These come as eye drops and gels, 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 may need to use them regularly to keep symptoms away.
There are several types of artificial tear drops and gels with different ingredients. Occasionally, 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.
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.)
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 are sometimes used to boost tear production by the tear gland and surgery is sometimes done to block the tears from draining away. Also, some people may need other treatments if they have an underlying cause for their dry eyes.
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.