Overnight contact lenses  which are only worn whilst sleeping may become the primary defence against the ever increasing incidence of short-sightedness, otherwise known as myopia. In just one generation, the probability of a child developing myopia has more than trebled and in parts of the world the condition has reached epidemic levels. Less than 20% of the Chinese population was short-sighted in the 1950s yet today, up to 90% of teenagers and young adults are whilst in Seoul, a recent survey revealed that 96.5% of 19-year-old men are short-sighted. By some estimates, one-third of the world's population - 2.5 billion people - could be affected by short-sightedness by the end of this decade.

Glasses, daytime contact lenses and laser surgery can correct short-sightedness but they do not address the defect causing the condition: an elongated eyeball which means that the lens focuses light from distant objects in front of the retina rather than directly on it. In some cases, this deformation stretches and thins the inner parts of the eye which increases the risk of retinal detachment, cataracts, glaucoma and even blindness. This is where overnight contact lenses  offer a breakthrough solution since they gently flatten the surface of the eye under the mild pressure of closed eyelids during sleep. This reverses the elongation of the eyeball and latest research has shown that by doing so these special lenses can prevent myopia from worsening.

For many years, optical science believed that myopia was largely down to genes but it has been clear for some time this could not be the whole story. Children are spending too much time watching TV, playing on computers and using smartphones - all near vision requirements believed to have influenced eyesight development. However, more recent research has highlighted the fact that insufficient exposure to outdoor light is a causal factor. Being around ten times brighter than indoor light, it is now recognised that spending more time outdoors is a key factor for children in mitigating other risk factors for myopia. However, once short-sightedness has been diagnosed, prescribing overnight contact lenses  ensures the myopia does not worsen any further.