While they may save you money in the short term, cheap, over-the counter reading glasses could end up costing your eyesight. While prescription lenses used to cost hundreds of pounds, competition within the market has brought the price of glasses and contact lenses down, and we’re now seeing a boom in the so-called ‘ready readers’ market – non-prescription glasses that are available from supermarkets and petrol stations for as little as £1 a pair. But can these glasses really compare to made-to-measure prescription glasses and contact lenses?

It’s easy to see the appeal of ready readers. Pick them up at the supermarket without the need for a lengthy eye exam, and at just a few pounds a pair, it doesn’t matter if you lose or break them. But wearing the wrong lens prescription can cause serious problems. Besides the hazards presented by not being able to see clearly, the wrong lenses can cause blurred vision, eye strain, headaches, dizziness, nausea, and even double vision.

The biggest problem with off-the-peg lenses, is that the centre point of the two lenses might not be aligned correctly. This can lead to serious eye strain, as it means that the sight in one eye might be clear while the other is blurred. The brain has to readjust the visual picture for you, trying to rebalance your vision, and this is what leads to strained, tired eyes, and in many cases, headaches too.

Ideally, the optical centres of lenses need to be around 62mm from each side of the lens. Many ready readers fail to meet this criteria, and depending on how near set or wide set your eyes are, the optical centre positioning may be completely unsuitable for your own individual eyesight.

While the cheap price tag may be a sight for sore eyes, this level of affordability often comes at a price. Poorly constructed reading glasses may have uncomfortable frames, unbalanced frames that can lead to head tilt, and may even simply start to fall apart within a few weeks. In some cases, the actual prescription of the lenses has been found to differ from the lens strength shown on the pack. Another issue to watch out for is cheap frames made from nickel, as nickel can cause skin allergies too.

But it’s not all doom and gloom. As the name suggests, ready readers are designed for reading. Those with a lower prescription may find that these over-the-counter lenses are just fine for correcting their vision for reading purposes, but just remember that they’re not designed for walking or other mobile activities. People with a higher prescription of +2 should test out these reading glasses for two minutes in order to check for any discomfort or vision issues, and to ensure that the optical centre points of each lens are aligned properly.

And remember that eye exams aren’t just a vital part of purchasing the right glasses or contact lenses prescription for you, they have an added benefit, in that they can help detect more serious vision problems, eye diseases, and more serious health conditions, such as diabetes and high blood pressure.