Q What do you think of Viscotears liquid gel (polyacrylic acid 2 per cent) for dry eyes? It is soothing when my eyes become very tired, and it does not appear to have side-effects except for temporary blurring of my sight. If polyacrylic acid is not a good idea, what do you suggest for dry eyes if the condition returns? - BF, London
A Tears are essential for eye health. The tear film, which consists of an oily layer, a watery layer and a layer of mucus, is spread over the eye by blinking. It keeps the surface of the eye smooth and clean, and carries oxygen and nutrients to the cells on the surface of the eye that have no direct blood supply. Without the tear film, good vision would not be possible.
Tear production normally decreases with age. Although dry eyes can occur in both men and women at any age, women are most often affected, especially after the menopause. In extreme cases, eye dryness can lead to damage to the cornea, the transparent covering of the eye.
Dry eyes can be caused by reduced tear production or increased evaporation from the surface of the eye. A dry environment or workplace, long hours at a computer, sun exposure, and smoking or second-hand smoke exposure can make eyes dry.
In people with rheumatoid arthritis, lupus and Sj"ogren's syndrome (a chronic systemic inflammatory disorder that affects the mucous membranes), the immune system attacks the tear-producing glands just as it does other body tissues, leading to dry eyes.
Conditions that reduce the cornea's sensitivity, such as diabetes, herpes eye infection and laser eye surgery (LASIK), also reduce blinking and tear production. A wide variety of common medications, including diuretics, beta-blockers, antihistamines, sleeping pills, sedatives and pain relievers, can reduce tear secretion, too.
Medicine has little to offer those suffering from dry eyes other than surgery to insert lacrimal plugs, which block the tear ducts and prevent tears from draining away too quickly, and topical wetting solutions. These 'artificial tears' are much less invasive, but the composition of the product is important.
Viscotears gel appears to be effective (Acta Ophthalmol Scand, 1997; 75: 457-61; Eye, 1998; 12: 839-47). But even though it is highly diluted, polyacrylic acid is a toxic and irritating substance. Viscotears also contains the irritating and potentially damaging preservatives cetrimide and sodium hydroxide.
It is widely acknowledged that most preservatives used in eyedrops and wetting solutions, including benzalkonium chloride and ethylenediaminetetraacetic acid (EDTA), are damaging to the eye (Arch Ophthalmol, 1995; 113: 371-8). So you might benefit by switching to a preservative-free product.
Many wetting solutions are mostly water and may not be as effective as natural tears. The tear film is mostly made up of mucus (Invest Ophthalmol Vis Sci, 1992; 33: 2006-11) and products like Viscotears use a synthetic gel as a replacement for this. However, it may be better to use a product containing ingredients such as electrolytes and bicarbonate (Arch Ophthalmol, 1995; 113: 371- 8) or cellulose-based lubricants that encourage the production of the natural mucus layer.
You may wish to try Can-C, a wetting solution that uses glycerine and carboxymethylcellulose sodium to lubricate, N-acetylcarnosine (NAC) - an eye-friendly antioxidant - and bicarbonate. It is made by IAS Limited (www.antiaging-systems.com) and is available in the UK from Life Long Products (tel: 0800 458 1771 or see www.lifelongproducts.com).
Other strategies include:
* using a humidifier, especially in the winter
* making an effort to blink more often
* resting your eyes periodically during the day.
You may also try looking to your diet. Artificial tears flush out debris, dilute substances trapped in the tear film and increase tear clearance. They do not, however, provide all the factors critical for the maintenance and repair of the corneal surface. These include antioxidants, particularly vitamin C (Curr Eye Res, 1991; 10: 751-9) and glutathione, an antioxidant composed of the amino acids cysteine, glutamic acid and glycine (Exp Eye Res, 1990; 150: 771-8), as well as beta-carotene (BMJ, 1992; 305: 335-9) and lutein (Am J Clin Nutr, 1999; 70: 509-16).