Having poor eyesight costs you money. Just how expensive it can be became clear last month after a survey published in Britain found that the average glasses wearer there spends more than £200 (€296) a year on frames, lenses and eye-care while those with contact lenses can expect to pay closer to £600, when check-ups, lenses, solution, and back-up glasses are factored in.

It is as costly in Ireland but there is one way the short-sighted with foresight can make dramatic savings - by shopping around online. Buying glasses on the internet, while possible, is problematic as it is next-to-impossible to gauge how a pair will look without trying them on. With contact lenses there are no such restrictions and it has grown into a big online business.

On the Specsavers website a six-month supply of all-day all-night lenses from Ciba Vision costs €155. On the VHI website, www.vhi.ie, bigger savings are to be found and the same amount of the same brand cost just €125. But it is by taking your business overseas that the real bargains can be sen. One US-based website, www.aclens.com, is selling a six-month supply of the same Ciba Vision lenses for just €91 including delivery to Ireland.

With prices like these, is it any wonder Irish consumers with their eyes on a bargain are starting to migrate. One optician PriceWatch spoke to said that they had noticed a significant drop in the numbers of people buying lenses recently and attributed the decline to online outlets taking the business.

"We launched the service in November 2004 and have seen huge growth in the numbers of customers," a VHI spokeswoman says about its online offering. "There was a 70 per cent increase in the number of customers from May 2005 to May 2006. We currently have between 700 and 800 new orders each month and this is growing all the time."

The VHI website, in partnership with a Dublin-based company called SoloOptics, has a price-match promise guaranteeing "that no other provider based in Ireland will have lower prices than us". And how do they do manage to cut prices so significantly? The company says that as a "primarily internet-based retailer, we have extremely low overheads. Bulk purchasing also means lower prices, which we pass on to the customer."

PriceWatch spoke to one devotee of online lens purchasing last week. He has been buying his lenses on the web for two problem-free years. "I get my lenses from a website based in Ohio in the US and they cost about half the price they used to. Every six months or so the company sends me a mail reminding me that I need to order more. The optician I used to go to is only two miles from my house and never once bothered to make contact with me to send me a reminder or anything else."

He says that he does get his eyes tested once a year "as it would be very foolish to stick something in your eyes that wasn't right for them". An added benefit of buying online is the absence of pressure, he says. "The great thing about buying online is that there is no hard sell. When you go into an optician, you almost always end up leaving with stuff you don't want - like designer frames or pricey eye drops. When you buy online it is anonymous and there is no pressure so you only get what you want."

It is not entirely problem free, however, and there can be risks involved in buying lenses from overseas. "Many online providers of contact lenses selling into Ireland are not based in Ireland," the VHI spokeswoman says, "and not subject to the same regulations as other Irish opticians. This causes significant concern for patient safety."

For people who do decide to buy lenses from companies based outside this jurisdiction, it is absolutely essential to have regular check-ups - at least once a year - to ensure your prescription is up to date and your eyes remain healthy. Specsavers insists users of its extended-wear lenses have a check-up every six months, which it provides free.

With any online supplier you will need your prescription details - Irish websites insist that you fax or e-mail scanned copies of the actual prescription to them before they will issue the lenses, while international sites have a more relaxed (and critics say less responsible) approach and just need the information.

You should be able to get a copy of your prescription from your optician and when sending on the details you will be asked to choose from a number of options. Typically this might be the base curve (the curvature of your eye), the diameter and the power of the lens required.

Globally, there are only a handful of manufacturers of contact lenses. Boots's daily disposable lenses, for example, are made by Bausch & Lomb. Identical lenses can be found at widely differing prices depending on the brand, so if you find the cheapest brand you can save a fortune, without compromising the quality, assuming of course that they are suitable.

When buying lenses it is also important to bear in mind that the longer the supply you buy, the cheaper it is - three, six or preferably 12 months' supply are common, although you should not buy more than a year's supply in case your prescription changes. On the VHI website, most users opt for the three-month option.

The VHI site insists orders will be dispatched only upon receipt of a contact lens prescription which has been issued within the past 12 months and it will supply only enough lenses to last the duration of the prescription. While international sites allow shoppers to circumvent this rule, it is not something that should be considered, as the cost of damaging your vision in the search for cheaper lenses would be considerably greater than the savings that can be made.