Consumer champion Which? posed as three different customers to order one pair of low prescription single-vision glasses, one pair of high prescription single-vision glasses and one pair of varifocals from nine online retailers.
It then worked with two opticians to measure the accuracy of the glasses received and assess whether they had been made to British standards.
Which? warned that, while ordering online can appear to be a cheaper way to buy glasses, consumers may be at risk of ending up with poor quality and potentially dangerous spectacles.
Seven of the 26 pairs of glasses ordered from online retailers failed the tests, either because the measurements were too far off what it had supplied and they did not conform to British Standards, or the lenses were loose and could fall out or be easily rotated. Two of the failed pairs were from Fashion Eyewear and two were from Goggles4U, with Spex4Less, Select Specs and Direct Sight each having one pair that failed. A total of 11 pairs of glasses ordered were criticised for their poor build quality.
Eight pairs had poor-quality lenses that were scratched, loose, warped or positioned badly, two pairs had issues with nose-pad positioning, and two had loose arms. For higher strength prescriptions, opticians recommend that customers should order high-index, thinner lenses.
However, Direct Sight, Fashion Eyewear, Goggles4U and Spex4Less failed to make this clear to customers, producing the higher prescription pair of spectacles with standard lenses that were considered to be much too thick.
The glasses from Direct Sight and Goggles4U were considered to be unusable due to weight and vision distortion.
While all nine pairs of glasses Which? ordered with a simple prescription passed the opticians’ checks, this was not the case for glasses with varifocal lenses. Seven out of the nine pairs of varifocals caused concern because no height measurements were taken, which could cause the wearer to experience vision distortion.
Glasses from Glasses Direct, Mister Spex and Smart Buy Glasses passed all the tests.
Natalie Hitchins, Which? head of home products and services, said: “Ordering online might seem like a convenient and cheaper way to buy glasses, but we’re warning shoppers to be wary.
“While simple prescriptions are less risky, our research shows that complex glasses, such as varifocals, might not meet the standards we would expect.”