Chiara Cavaglieri checks out the low-price claims of the online lens stores

There are about 3.5 million contact lens wearers in Britain. If you're one of them, you may well be paying too much for them, or at least that's what online retailers such as and say. Websites such as these offer heavily discounted contact lenses by buying them directly from the manufacturers in bulk and selling them on from warehouses. Without the cost of opticians' salaries and expensive premises, they can offer far more competitive prices on lenses from all the big manufacturers: Johnson & Johnson, Ciba Vision, Coopervision and Bausch & Lomb. "Generally, what we've found is that it is cheaper to buy online; the biggest saving we uncovered was £52.50 on a three-month supply of contact lenses," says Matt Clear from Which?.

The biggest savings will be for those willing to sacrifice a large initial outlay and buy in bulk at one of the specialist discount websites. Purchasing a year's supply can save an astonishing amount of money, although it is not advisable to pay for more than this in case your prescription changes. At GetLenses, 360 pairs of Ciba Vision Focus Dailies comfort lenses would set you back £199.65, while in a Specsavers store, a year's supply of premium daily lenses, which are in essence the same lenses, jumps to £264 – more than £60 more expensive.

Savings are less clear cut with monthly contact lenses. At Optical Express, AirOptix lenses from Ciba Vision cost £60 for six pairs, which last six months, while at the same supply costs only £39. Again, online beats high street. However, whereas high street providers include solution in their price, online suppliers often don't. As three months' supply of solution can cost anything from £10 to £20 it's easy to see how sometimes online can prove more expensive than the high street. The message is shop around with care.

Purchasing contact lenses online is straightforward. All you need is a contact lens prescription; the optometrist can recommend particular lenses for you. The prescription will include three key numbers: the base curve, overall diameter and spherical power. But there are caveats to buying online. Lenses should fit properly as well as comfortably, and your general eye health should be checked regularly, so keep up your annual visits to the optometrist.

"The importance of having regular contact lens check-ups cannot be overemphasised. Contact lens wearers should not change their prescribed lens type, wearing schedule, replacement frequency, solutions or care procedures without the recommendation of their eye care practitioner," says Alison Ewbank, a spokeswoman for the British Contact Lens Association.

These check-ups costs between £20 and £30; if the online savings do not exceed this amount you may be better off buying on the high street. What's more, several high-street providers offer incentives. At Specsavers, customers are entitled to two free pairs of contact lenses each month to replace any that are damaged or lost.