Dry eye is a term used to describe a variety of eye conditions where there is either not enough production of tears or too much loss of tears from evaporation. Dry eye can cause damage to the surface of the eye and is associated with symptoms of eye discomfort. Dry eye becomes more common with age and affects 15-33% of those over 65. Women are affected more than men by dry eyes.

If you have dry eyes, you may feel that your eyes are ‘gritty’ or burning. You may also be sensitive to bright lights and experience slight blurring of vision. However, dry eye is not a condition of the retina (the ‘seeing’ part of the eye) so you will not suffer permanent damage to your vision. Sometimes dry eye can lead to excess tears – which seems a bit odd but is the brain’s way of compensating for lack of tears (it produces more). These ‘emergency’ tears do not lubricate the eye in the way that normal tears do.

Dry eye is caused by various factors other than aging. Certain medications, like diuretics and beta-blockers, may cause dry eye. Dry eye is also the prime symptom of Sjögren’s syndrome, an autoimmune disease affecting the tear glands. Dry eye is treated by applying some kind of tear replacement fluid. But tears have unique properties which are hard to reproduce in such products. They must have a good lubricant effect, they must have a long retention time in the eye, they must not irritate the eye and, of course, they must not interfere with your vision. Many existing medications for dry eye are based upon cellulose compounds which are too watery and have a poor retention time – so you need to keep re-applying them. Another component used in dry eye medication is carbomer which is rather viscous, making it hard to apply.

A new product for dry eye, called Rohto ® Dry Eye Relief contains hyaluronic acid (HA), a component of many body tissues, including the eye itself. It protects the eye by being able to bind in water and has the interesting property of being more viscous when the eye is still and less so when the eye blinks, which makes for a more stable tear film. The effect is enhanced with the addition of tamarind seed polysaccharide (TSP) to Dry Eye Relief. In a clinical study, TSP plus HA increased patient eye comfort and improved the condition of the eye surface more than HA alone.

Sources:

Rohto ® Dry Eye Relief launch, London, 1^st December 2009
Dry Eye Syndrome http://www.nhs.uk/Conditions/Dry-eye-syndrome