Dry eye syndrome

Dry eye syndrome 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.

eye with eyelid detail
tear film


Diagram of the eye and tear production
Tiny glands in the eyelids (meibomian glands) make a small amount of lipid 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 eye syndrome can affect anyone, but it becomes more common with increasing age. Dry eyes affect about 15 to 33 in 100 people, ie possibly 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 antidepressants.
      • Antihistamines.
      • Some treatments for anxiety and other psychological problems.
      • Beta-blockers such as propranolol, atenolol.
      • Some treatments for acne, etc.
      • Some eye drops used to treat other eye conditions.

This is not an exhaustive list. Tell your 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, 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.

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.

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 puncture (perforate).

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.