Article extracted from Understand More About Dry Eye Syndrome, a publication of the Singapore National Eye Centre, a member of the SingHealth group.
  

What are tears and why are they important?

Tears are not just emotional indicators comprising salty water. They are a complex mixture of oil, water and mucus, created by three different “production factories” in the eye for its own benefit.

The mucus is made by microscopic goblet cells in the conjunctiva and the water layer by the lacrimal gland under the orbital rim bone, just below the eyebrow. The outermost layer, oil, is provided by the meibomian glands that line the edges of the eyelids. This mixture coats the entire surface of the eye, cleaning, lubricating and nourishing it throughout the day and protecting it from infection.

Sufficient quality and quantity of tears are essential for good vision, as they maintain a healthy and clear refractive surface. When there are not enough tears, or when the tears don’t have the correct mix of oil, water and mucus, the condition called dry eye syndrome occurs.

Dry eye syndrome: Causes

Dry eye syndrome is part of the natural ageing process, so the elderly are more likely to develop it. Also prone to it are those going through hormonal changes.

People suffering from certain ocular and systemic diseases such as rheumatoid arthritis, diabetes and thyroid problems, and those on medication such as antihistamines, decongestants, blood pressure pills and antidepressants, are also more likely to have dry eyes.

Lifestyle too can play a part. Constant exposure to smoke, wind and dry environments may also lead to dry eye. The condition is easily missed. Those who have it may not be aware of it because its symptoms can be thought to be due to fatigue or tiredness.

Dry eye syndrome: Symptoms

Symptoms of dry eye syndrome include red or irritated eyes, eyelids which feel heavy or have a sensation of sand or a foreign object in the eye, occasional blurring of vision, and watery eyes which may be secondary to irritation of the eye.

The nerves on the surface of the eye (cornea) are extremely sensitive to many types of stimuli, including dryness, tiny changes in temperature, and particulate matter. Some of these nerves relay signals to the tear-producing glands as well, causing reflex tearing.

Dry eye is also one of the leading causes of contact lens intolerance or discomfort, as contact lenses can destabilise tears. This can lead to irritation, due to dry eye, hypoxia, or to lens protein deposits, and immune responses to these deposits.

Read on to find out how dry eye syndome is diagnosed and easy remedies.