When did you last blink? Chances are, you couldn't say. For most of us, our eyes are something that we take for granted. We blink without realising we are doing it, and rarely give a second thought to whether our eyes are lubricated or our tear ducts are functioning.
For a significant minority of the population, however, the eyes can be a constant source of discomfort and even misery. Dry eye - a condition characterised by dryness, itching, discomfort and a feeling of grittiness (as though there were a grain of sand caught in them) - is a remarkably common complaint, especially in the UAE. At its worst it can even involve photophobia, blurred vision and the sensation of heaviness in the eyes.
"I have nearly scratched my eyes out," says Finn, 41, an Irish expatriate living in Abu Dhabi, who suffers from dry eye and preferred not to share his surname. "It can be very uncomfortable and make you look as if you are crying all day. I get marks on my face if I scratch too much."
Some studies have suggested that between 17 and 30 per cent of people experience dry eye syndrome at some point during their lives, and as many as nine times more women than men are affected. The numbers may well be even higher in the UAE, where the condition is particularly prevalent.
According to Dr Andrea Sciscio, consultant ophthalmic surgeon at the Moorfields Eye Hospital in Dubai, it is one of the most common complaints presented by patients at the hospital.
"There are no official figures," he says, "but in our clinics, the incidence is around 20 to 25 per cent. We do see a high number of patients with dry eyes and there is no doubt that a lot of patients do benefit from tear-replacement drops here in Dubai when they never had problems before."
Part of the problem in the UAE is the climate.
"There is no scientific analysis of the air quality here," says Sciscio, "but it is very clear that anybody who has problems with the outer surface of the eyes feels a lot better when they are in a northern European country. Undoubtedly, the microclimate that is present in the UAE and in particular in Dubai affects the fine balance between how many tears are produced and how many drain into the tear channels. The hard conditions, due to the high temperatures and the constant and high air flow of the air conditioning systems do allow the tears to evaporate from the surface of the eyes."
Dry eye sufferer Emma Buckingham, 21, a Scottish expatriate studying in Abu Dhabi, agrees that air conditioning makes her dry eye worse. She also finds the lack of moisture in the air an aggravating factor.
"On very humid days [my eyes] don't seem to get itchy at all," she says. "However, on very dry days, instead of them just being itchy in the evenings, it can start around midmorning. The UK seems a lot better because it's so damp all the time."
So what exactly is this condition that creates so much discomfort? Dry eye is a term used to describe a variety of eye conditions in which there is either insufficient production of tears or excessive loss of tears from evaporation; it can even involve a complex combination of both.
The problem is centred on the tear film that normally keeps the eyes moist and lubricated. In healthy eyes, tears create a lubricating and cleaning film over the eye. If this film is insufficient in quantity or composition, the result is dry eyes.
Its causes vary widely from person to person. For many, it can simply be caused by environmental factors. Heat, dust, air conditioning, air travel, contact lens wear and failure to remove eye make-up at night can all contribute to the condition. Driving and computer use can also be problematic, as both are associated with a low blink rate, often combined with opening the eyes wider than normal; this can dry out the tear film over the eye.
For others, age is a factor. People often make less tears as they get older, and some women notice dry eyes developing around the time of menopause.
Dry eye can also be caused by some medication. Diuretics, some antidepressants, antihistamines, anxiolytics, the contraceptive pill, betablockers and some eye drops used to treat other eye problems can lead to dry eye.
It can also be a symptom of a number of medical conditions, including severe vitamin A deficiency, eye trauma, herpes eye infection, diabetes and an autoimmune disease known as Sjören's syndrome that results in inflammation in the salivary and lacrimal glands, leading to severe dry eye.
Although most people rely solely on eye drops known as artificial tears to treat the condition, because dry eye can reveal an underlying medical condition it is wise for sufferers to seek professional advice.
"It is important to be checked at least once," says Sciscio. "Rarely, but usually with more marked cases, there can be associations with disease elsewhere in the body."
Apart from applying eye drops, sufferers of dry eye tend to rely on simple, homespun solutions. Heather Roberts, 58, a South African registered nurse who lives in Dubai, says that she works around her dry eye.
"I make massaging my eyelids part of my daily face-cleaning routine," she says. "It seems to improve the dryness and I have found my eyelashes have grown longer."
Roberts also recommends wearing glasses or a hat with a peak to stop the air conditioning from doing too much damage. Others recommend bathing the eyes in water or even in tea to obtain temporary relief.
All are agreed that while uncomfortable and inconvenient, a positive approach to the condition is required.
"It's not something that will ruin your life," says Buckingham. "To be honest, it doesn't really change a lot. You just have to be careful."
Roberts agrees. "Don't let something like this ruin your life," she says. "In the grand scheme of things, it is not life-threatening."