New research suggests that cheap reading glasses might be readily available, but in the long term they can cost you your eyesight.
By the age of 50, most adults have problems reading a book or newspaper without spectacles, so the arrival of the cheap glasses in supermarkets, high street stores and market stalls less than ten years ago has been seen as a saviour for many.
To avoid paying 100's of pounds for a pair of reading glasses from an optician that might easily be lost or broken, many buy several cheap versions to stash around the house so that they can always find a pair.
A researcher at consumer champion 'Which?' checked 14 pairs from seven high street chains and found that those carrying a higher prescription – plus 3.5 to plus 4 – considered to cause the most concern.
"Off-the-peg glasses could cause eye strain, blurred vision, headaches or double vision," The Daily Mail quoted the researcher as saying.
"For people with higher prescriptions, they're not suitable for walking or other mobile activities. They could even 'cause a nasty accident," he added.
The biggest problem is non-alignment, which means that the sight in one eye might be clear while the other is blurred.
"This could cause eye problems or a head tilt," the researcher said.
Opticians say eye examinations are essential before buying glasses. As well as ensuring the correct prescription is used, they can detect serious health issues, such as cataracts and brain tumours.