Night Vision - A revolutionary type of lens can correct eyesight while you sleep - And it's been around for decades, says Alice Hart-Davis.

Using contact lenses to correct short sight is a pretty straightforward procedure. You put the lenses in during the day to sharpen your vision and take them out at night. Perfectly simple. But now, an extraordinary type of lens is hoping to turn this state of affairs upside down.

The UK is deeply in love with soft, disposable lenses (soft lenses accounted for 97 per cent of new lens fittings in the UK in 2007) and we rip open a million new disposable lenses every day, more so than anywhere else in the world. The newcomer in the optical market place is in a rather different mould. It's rigid, you definitely don't throw it away and you wear it overnight. It works by reshaping your cornea to give you better vision so that you don't have to wear lenses during the day.

At first, this approach sounds somewhere between bizarre and impossible, but orthokeratology, to give the practice its proper name, has a legitimate and serious history. The correction to the eye is made in roughly the same way that braces can be used to correct crooked teeth; the cornea is malleable and will, overnight, assume the fractionally different contours into which the lens has forced it. The difference is that while corrected teeth stay in their new position, the cornea is highly elastic and, after 24 hours, will have returned to its original shape, so to maintain the correction the lenses have to be worn every night.

One interesting aspect of orthokeratology is that many optometrists feel they slow down the process of short-sightedness, especially in teenagers. This remains clinically unproven, but the technique has won the support of the respected Institute of Optometry. It is not a long-term solution to short sight but for people who find lenses difficult to wear during the day, it is seen as an attractive alternative to normal lenses and simpler and cheaper than laser surgery. Surprisingly, the technique has been available since the 1960s, but has been both expensive and complicated.

However, now that the technology has advanced to allow extremely detailed measurements of the cornea, it is becoming a possibility for the mass-market at a price where it can compete with daily disposables.

There have been various attempts to convince the public that orthokeratology is the answer to their vision problems so far, it hasn't caught on. The name hasn't helped and the new company, i-GO, has had the wit to give their system a more comprehensible name: ‘Overnight Vision Correction'. "It's orthokeratology by a new name," says Andrew Gasson. "But this time using a very good design for the lens and yes, absolutely, orthokeratology does work. It is the contact lens answer to laser."

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