Two factors inspired Mike Duthie, an engineer living in Aberdeen, to develop Airshield. The first was the way hay fever afflicted his wife, Jo, who is a keen gardener. The second was the sight of joggers and cyclists with personal stereos, their activities apparently unhindered by the apparatus.
The Airshield spectacles have hollow frames pierced with a series of holes. A small, battery-powered pump, about the size of a Walkman, takes in air, which is passed through a filter to remove pollen and other particulates, and then pumped out through the rim of the spectacles.
The series of holes is designed to maintain a slightly higher pressure than the surrounding pollen-laden air, preventing it getting near the wearer's eyes.
About 20 per cent of the population suffers from hay fever. It is caused by exposure to pollen, and can be aggravated by dust, smog and other airborne pollution.
Microscopic pollen grains entering the eye trigger a reaction in which a substance called histamine is released from cells in the skin and mucous membranes of the eyes, nose and throat. This causes watering and itchiness of the eyes and constriction of the nasal passages. The reaction can cause extreme discomfort.
The most common form of treatment is antihistamine drugs that block the effect of histamine. Unfortunately, one side-effect may be drowsiness. Some sufferers are desensitised by having annual injections of the offending allergens to build up resistance.
'Airshield is effective because a pollen-free and pollution-free zone is created between the eyes and the lenses of the spectacles,' said Stewart Todd, a director of Duncan and Todd, optometrists, which has spent pounds 350,000 in the development of Mr Duthie's idea. 'For the millions of people who want fast, drug-free relief from hay fever symptoms, it is an effective alternative.'
A clinical trial carried out by a consultant immunologist, Martin Stern, at the Midlands Asthma and Allergy Research Association in Leicester, concluded Airshield 'provides a practicable and effective method in the management of allergic conjunctivitis (hay fever)'.
The Italian-designed Airshield frames can be fitted with plain or prescription lenses, clear or tinted. They need to be fitted by an optician because the frames must sit close to the brows and have justa little clearance at the bottom if the positive air pressure is to be maintained. The pump, which can be worn on a belt, has batteries that last about 25 hours and a fibre air filter that must be replaced weekly.
Duncan and Todd suggests that Airshield could have health and safety applications, where workers are exposed to toxins or irritants. Airshield is also said to prevent tears when peeling onions.
Mr Todd said he had made another discovery on the ski slopes, where Airshield cured the problem of glasses fogging over when worn under a ski visor.