We all know the old warning — you should never stare into a laser pointer. But is it really dangerous, or is it just another old-wives tale from a more modern age? Spoiler alert: it’s not. You really shouldn’t stare into a laser pointer.

A cautionary tale

Image credits: Androudi and Papageorgiou/NEJM.

The parents of a 9-year-old boy in Greece were concerned after the boy could no longer see properly with one of his eyes. They took him to a clinic, and tests showed that while the boy could see excellently with his right eye, the same couldn’t be said about his left eye. When the doctors examined him more thoroughly, they found a large hole in the macula — the central area of the retina where the light is focused in front of the eye. The boy had managed to burn a hole in his retina after repeatedly staring into a laser pointer.

Holes in the macula aren’t that uncommon in the elderly, but there’s no reason for such a problem to occur in a child. However, retinal injuries due to laser pointers have become so common that there’s actually diagnostic criteria for determining if the problem was indeed caused by one of these devices.

It doesn’t take long for the damage to take place, either. While it’s not clear what was the exposure of the boy in Greece, doctors reported a different case in 2012 where a 5mW laser pointer caused significant damage to a 13-year-old boy’s eyes after just one minute of exposure. His eyes healed, which is often, but not always, the case.

In 2015, another 13-year-old boy was unlucky enough to have a 50 mW laser shined into his eye for just one second, permanently damaging his retina.

In the US, lasers are limited to 5 mW, and in most places in Europe, legislations are even more stringent, limiting the devices to just 1 mW. You need a permit for anything stronger. But the legislation isn’t strongly enforced and it’s easy to buy a strong laser on the internet. Many lasers are also purchased via street vendors, and they can be mislabeled or not have any label at all.

In the case of the boy in Greece, it’s unclear if the damage is permanent. After 18 months, his vision was still damaged and it may never recover. The takeaway is clear: you should never ever stare into a laser pointer — your mom was right.

The study was published in The New England Journal of Medicine.