Eye health: Dry eyes

The eye depends on the flow of tears to provide constant moisture and lubrication to maintain vision and comfort. Tears have a combination of water for moisture; oils for lubrication; mucus for even spreading, and antibodies and special proteins for resistance to infection. These components are secreted by special glands located around the eye. When there is an imbalance in this tear system, a person may experience dry eyes.

When tears do not adequately lubricate the eye, a person may experience:

• Pain
• Light sensitivity
• A gritty sensation
• A feeling of a foreign body or sand in the eye
• Itching
• Redness
• Blurring of vision

Sometimes a person with a dry eye will have excess tears running down their cheeks, which may seem confusing. This happens when the eye isn't getting enough lubrication. The eye sends a distress signal through the nervous system for more lubrication. In response the eye is flooded with tears to try to compensate for the underlying dryness. However these tears are mostly water and do not have the lubricating qualities or the rich composition of normal tears. They will wash debris away, but they will not coat the eye surface properly. Because these emergency tears tend to arrive too late, the eye needs to regenerate and treatment is necessary.

What causes dry eyes?

As well as an imbalance in the tear-flow system of the eye, dry eye can be caused by the drying out of the tear film. This can be due to dry air created by air conditioning, heat or other environmental conditions. Other conditions that may cause dry eyes are:

• The natural ageing process, especially during menopause
• Side effects of using certain medicines such as antihistamines and contraceptive pills
• Diseases that affect the ability to make tears such as Sjogren's syndrome, rheumatoid arthritis and collagen vascular diseases
• Structural problems with the eyes that don't allow them to close properly or a problem with the tear ducts

Ask your doctor what you can do to help prevent dry eyes occurring. Your doctor may recommend you see an optometrist (an optician who examines eyes, tests sight and prescribes and dispenses glasses and contact lenses). If the diagnosis is uncertain, your doctor may refer you to an ophthalmologist (a medical doctor who specialises in eye care and surgery).