LASER pens shone at aircraft cockpits do not pose a danger to pilots' eyesight but the dazzle could lead to a "devastating" crash, eye experts have warned.

There have been more than 1500 laser pen attacks on planes in the UK over the past year, including one high-profile incident in February where a Virgin Atlantic jet en route to New York had to turn back when the co-pilot began feeling unwell following a laser beam strike on the cockpit.

And in March this year, a lecturer was jailed for 14 months for "culpably and recklessly" shining a laser pen at the Police Scotland helicopter flown by Clutha pilot Captain David Traill, forcing him to take evasive action. The incident occurred on November 28 2013, just 24 hours before Captain Traill died in the Clutha helicopter crash in Glasgow.

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However, specialists writing today [wed] in the British Journal of Ophthalmology said there is "no evidence" to suggest that lasers pointed at cockpits damage pilots’ eyesight, as they are only harmful at relatively short distances.

They said the only reported case of a pilot supposedly being blinded by a laser beam attack on a cockpit was "suspect" because there would have been "insufficient energy [entering the eye] to produce irreversible damage".

While downplaying the health implications of laser pens at such high altitudes, they stressed that the "totally unacceptable" risk came from the glare distracting the pilot during hazardous manoeuvres such as take-off or landing.

The Herald:

They write: "In this situation, the systems are operating over a long range - typically hundreds to thousands of metres and the laser beam has to pass through the atmosphere before traversing a cockpit canopy or windshield.

"These are usually pitted or scratched and will serve to scatter the primary beam and may result in the generation of secondary and tertiary beams.

"In these situations, pilots tend to self-focus on a sudden bright light in the cockpit environment and may be dazzled resulting in an after-image and almost certainly will be distracted.

"Obviously, if such a distraction occurs at a critical time such as during landing then the result could be devastating."

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Between half and one million laser pointers, pens, and key rings are thought to have been in circulation over the past decade, but the authors stress that the potential dangers to eyesight at short distances on ground level means some stronger items should be banned from public sale.

They write: "In the past, pointers predominantly produced red laser beams and were restricted to have an upper output limit of one milliwatt and as such were classified as class two laser products. "Safety was afforded by insufficient energy being able to pass into the eye before the targeted individual blinked and turned their head.

"In reality, as a result of both increased efficiency of modern devices and poor manufacturing compliance many of these devices classified as class two have outputs of between 0.5 and 300 mW. "Clearly, they are mislabelled and should have been identified as class 3B laser products, which are not appropriate for general sale to the public.

"Today, low-cost laser ‘pointers’ producing green or red laser beams with output powers of 1000 mW can be found and indeed devices on the internet of between 1500 and 6000 mW are commercially available.

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"These class four devices are capable of causing irreversible retinal damage if directed into the eye over short ranges, up to several metres.

"Such devices have resulted in foveal [eye] injuries in children with current estimates of 150 cases in the UK."

Stephen Landells, flight safety specialist for pilot's union, Balpa, said: “People need to realise that shining a laser at an aircraft endangers the passengers, the crew and people on the ground.

"Pilots are concerned not only about the potential eye damage, but also about how attacks at a critical phase of flight can startle and cause serious distraction.

“Pilots understand there are some important uses for lasers but can’t see any good reason why people should be allowed to carry one when there is no obvious purpose for doing so.

"BALPA has called for all but the lowest powered lasers to be restricted and wants them recognised in law as potential weapons in the same way knives are.

"This would mean police would have improved powers to search people they suspect are carrying a laser, confiscate it and arrest them unless they have a good reason for having it."