When Celine and Ben Jackson bought their son William and his two brothers laser pens for Christmas, they believed they were innocent stocking fillers, the type of toy they had enjoyed playing with safely before.
But on Boxing Day, after using one of the devices, William began to complain of an uncomfortable sensation in his left eye.
The 10-year-old schoolboy, from Wadsley, was checked by an optician and referred to the Royal Hallamshire Hospital, where consultants found inflammation on the macula, the vital central area of the retina at the back of the eye.
William’s eyesight then began to quickly deteriorate, causing his parents to fear he would be completely blinded.
However, the youngster was prescribed steroids which reduced the swelling inside the eye, and now his sight has recovered - but Celine said there is likely to be permanent scarring.
The Jacksons are now backing consultant opthalmologists at the Hallamshire and Sheffield Children’s Hospital, who have completed the first study of its kind into paediatric patients seen for injury to their eyes triggered by novelty laser products.
Experts say the lasers can be much more powerful than labels on their packaging suggest.
“It was frightening, we felt dreadful,” said trainee health visitor Celine, 42.
“We didn’t know whether he’d be completely blinded. He has quite bad eyesight anyway, and his sight deteriorated quite rapidly. There was a period when he was in school and he couldn’t see boards and books. Everything had to be a massive font for him to see it.”
Celine said the lasers were bought from the internet in 2012 for William and his two brothers, aged 13 and 8, as they had enjoyed playing with similar toys before.
“They were red, green and blue lasers, the type of thing used to point things out on a chart.”
William, a pupil at Sacred Heart Primary in Hillsborough, could not remember the light being shone in his eye, but medics believed the device caused the injury.
It took around six weeks before his sight was restored, but he still needs to use vision aids such as magnifying glasses, particularly when tired.
“It seems to be something that’s used in an innocent way, but the consequences to a child can be far-reaching. Now if we see children with a laser pen we tell them to bin it.
“William will agree, he just doesn’t want anybody else to go through it.”
The Sheffield study was carried out over 18 months, and all of the patients were from the city, aged eight to 15.
Another child who took part - an eight-year-old boy - has been left with permanent laser scars, which he can see constantly at the centre of his vision. In his case, the laser beam was flashed in his eye for no more than a few seconds.
This has dramatically reduced his vision - he can now only read the largest letter on a standard optician’s chart from three metres, whereas a person with normal sight can do this from 60 metres.
Mr Fahd Quhill, consultant ophthalmic surgeon at the Hallamshire, said: “Misuse of these products can lead to irreversible damage to the eye.
“The retina is very sensitive and once damage is done, it is irreparable. This can impact on children’s futures with normal activities being compromised such as reading, recognition of faces, driving or playing sport.”
Public Health England says lasers sold to the public for use as pointers should generally be restricted to class one or two devices - less than one milliwatt in power.
Mr Quhill added: “One of the laser pointers that caused the retinal damage in one of our child cases was 72mW and all measured were more than 40mW of power and thus Class 3B.”
The research was published in Eye, the journal of the Royal College of Opthalmologists.