Ewwwcrrsssh! The screech of metal against wood was the moment I began to question the efficacy of miraculous-sounding contact lenses that correct impaired vision while you sleep. I was not asleep, in fact I was reversing my car, but my vision was definitely still impaired because I had just reversed into a telegraph pole. Perhaps I should have blamed my foolish decision to reverse down a dark country lane but I decided to berate my new i-GO contact lenses ("sleep, see, go"). One week into my trial and, by evening, everything was a bit of a blur.

If you have ever worn contact lenses, the idea of wearing them to sleep in is not just revolutionary, it is repulsive. Ask any contact-lens wearer who has woken from a boozy night out to find their eyelids gummed up and lenses screaming to be removed from bloodshot eyes.

But i-GO lenses are deliberately popped in at night, and removed in the morning. A new generation of gas-permeable lens, they allow oxygen into your eyes during wear, preventing your eyes from becoming dry and sore. Crucially, however, they encourage movement of cells in the epithelium, the top level of your cornea, from the centre of your eye to the periphery. These cells are gently shifted by the fluid - the tear film - between contact lens and cornea, temporarily creating a new structure to the eye.

This "overnight vision correction" treatment is called orthokeratology and the lenses are now available in ordinary opticians in major cities across England. It sounds amazing, and means you can see during the day without the need for glasses, contact lenses or laser surgery.

When I meet Kieran Minshull, my optician for the trial, at LK Leon in central London, I wonder why he's wearing glasses. Minshull, it transpires, has even worse sight than me and i-GO lenses cannot correct short-sightedness worse than -5.0 (Mine hovers at -4.0). And these lenses do not correct serious astigmatism. Are they dangerous? "No more than with normal contact lenses," says Minshull. "Hygiene is important but there aren't any side effects." Unlike laser surgery, there are no permanent changes. If you don't keep wearing the lenses at night, your eyes readjust and your vision returns to how it was within a few days.

Minshull has treated 18 people since the i-GO lenses were launched in the UK but in the US, 50,000 people are using this technology. The lenses cost from £200 for the initial appointments and fittings and £40 per month for lenses, checkups and solutions.

I begin with a sight test, then Minshull takes a topography of my eye, photographing the curvature of my cornea to obtain the measurements needed to make the lenses.

A week later, Minshull shows me how to put in and remove the lenses - easy if you are familiar with contact lenses. And he tells me that I need to sleep regularly, for six hours, and wear them every night. I have some solution to clean and store them in, and lubricant should they become stuck in my eyes (urgh) and that's it. Or so I thought.

These lenses, I am told, do not usually work instantly. "We should achieve something like a 70% change within the first night of wear," says Minshull. In the early days, most users find their eyesight deteriorates by the end of the day. "You may notice a little bit of ghosting in the evening," he says. I am supplied with some -1.50 daily disposable contact lenses in case my eyesight becomes less than perfect.

After the first night, I wake up and visit the opticians again, for a checkup, with the i-GO lenses still in my eyes. Everything is blurred and very uncomfortable because I am unused to these hard, plastic gas-permeable lenses. It turns out my vision is about 70% better and I return to work wearing soft contact lenses to correct my improving vision. Things are still rather blurry. I accidentally blank people I know. I am not enjoying blurred vision. It makes you appreciate the miracle of sight.

After two nights in the lenses, I wake up and - hosanna! - I can see. Without lenses. Almost perfectly. The problem is at night: when it gets dark, I realise that while I can read car numberplates at a distance, my sight is distorted by electric lights, which are almost as blurry as if I had my normal vision. Street lights and car headlights are fuzzy.

At my weekly checkup, Minshull explains that this "ghosting" or halo effect occurs because, while the lenses have corrected the centre of my pupils, they have not yet altered the periphery. This means that in low light, when my pupils widen, I am seeing with the corrected zone and with a small uncorrected area. With most clients, this passes in time. After my very minor crash, though, I decide to wear my i-GO lenses when I am driving at night. They are not as comfortable as my old soft contact lenses but are tolerable and I can see pin-sharply with them in.

At the end of the four-week trial, my eyesight only declines very slightly during the day but in the dark, bright lights are still distorted. I return for my final checkup ready to give up the lenses but Minshull shows me the progress on reshaping my eye, and says that in some cases it can take longer than four weeks. We continue for two more weeks but the i-GO lenses still leave me with blurred vision at night. Minshull believes they have not worked because I have unusually large pupils.

Sean O'Sullivan, 44, a business manager for a software company, has been using the lenses for three weeks. His prescription (-3.75) is similar to mine and yet his right eye was perfect after one night and his vision in both eyes was perfectly corrected after two nights. He, too, experienced blurry lights after dark but this has steadily lessened. He can still see late at night and, if he has to travel to America, into the next day as well. "It's an amazing thing to think that by putting a plastic lens in your eye at night you can see for a day and a half," he says. "I'm surprised more people aren't trying it. It is very liberating. It feels like a miracle cure. If it works, it's a great alternative to laser surgery."

So far, only one other of Minshull's patients has experienced a similar problem to mine and they loved days without lenses so much they persevered. And I can see the attraction: it was wonderful to hurl myself into the ocean and not worry about contact lenses, do away with the dryness and red eyes from wearing ordinary contact lenses all day, and nice not to worry about treading on, or losing, my glasses again. But I am letting my eyes return to their old prescription because of the blurring at night. I could wear my i-GO lenses after dark, when I am awake, but that that seems little more convenient than using standard contact lenses.

I feel sorry for Minshull, who looks crushed when I tell him they are not working for me. He has taken me through the trial with reassuring thoroughness and admirable patience. But I've had it with newfangled contact lenses. On the way out of LK Leon, one of their swish pairs of frames catches my eye and I try them on: I can definitely see myself wearing glasses again.

igolenses.com, 0844 7362579.