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UK: Consumer lasers hazardous up close, but will not injure pilots, say 3 top UK experts

Three top U.K. laser safety experts published an overview of consumer laser hazards in the April 19 2016 British Journal of Ophthalmology. The key finding that made news (at sources such as CNN, ABC and the Daily Mail) was that lasers aimed at aircraft have not caused eye injuries to pilots, and are not likely to do so.

But in addition to this declaration, the authors also provided a succinct summary of the current state of consumer laser pointer misuse, and how ophthalmologists should proceed when studying a patient’s laser exposure.

Experts John Marshall, John O’Hagan and John Tyrer began by noting that low-powered Class 2 (less than 1 milliwatt) and Class 3R (1-5 mW) lasers “are not an eye hazard, and even if used inappropriately will not cause permanent eye damage.”

However, consumer laser devices with Class 3B (5-500 mW) and Class 4 (above 500 mW) powers have begun to cause injuries. “….[C]lass 4 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 injuries in children with current estimates of 150 cases in the UK. The [UK] media has given significant coverage to this growing problem.”

Ophthalmologists were advised that in cases of close up exposure, there may potentially be permanent damage. A detailed examination would be warranted, although there is no treatment to reverse permanent damage.

The hazards from this short range misuse differ from the hazards of aiming a laser towards pilots. Because the laser-to-aircraft distance is typically “hundreds to thousands of metres”, and because of scattering from the windscreen, eye injuries are nonexistent: “Fortunately, these exposures are at irradiances that are incapable of producing irreversible retinal damage even at distances of 100 m.”

They said that only one case of alleged retinal damage has been reported in pilots. [LPS.com note: this is for publicly available reports involving civilian pilots.] The experts concluded the case is suspect for a number of reasons; they do not believe laser targeting caused the alleged injury.

Marshall, O’Hagan and Tyrer turned from injuries to the hazards of distracting pilots with bright laser lights: “Obviously, if such a distraction occurs at a critical time such as during landing then the result could be devastating.”

For ophthalmologists examining pilots, if there are no permanent abnormalities on an Amsler grid test, the physician should not do any detailed eye exam, as this “would only serve to compromise the pilot's vision for a longer period.” The authors noted that pilots may delay seeing an expert for “many hours or a day or so during which there may be a growing psychological element.”

In an interview with CNN, Marshall said the findings on pilot hazards are based on previous laser safety research as well as a new study done with field experiments at a military base over about three years.

In the BJO editorial, the three experts agreed that current laser safety standards and guidelines are based on valid experiments and science. The standards do not need to be revised, “…but clearly further attempts must be made to educate the public.”

The editorial concluded “The European Commission has mandated the European Standardisation bodies to produce a standard specifically for consumer laser products. This should allow enforcing authorities to remove unsafe products from the market. However, compliance by manufacturers will remain an issue, as will direct imports by the public purchasing unsafe laser products over the internet.”

From the British Journal of Ophthalmology editorial “Eye hazards of laser ‘pointers’ in perspective” by John Marshall, John O’Hagan, and John Tyrer, available in HTML text and as a PDF document. Click on the blue “Read More…” link below for an April 19 2016 press release from the BJO summarizing the paper’s findings relative to pilot hazards.
The blue text is a press release from the British Journal of Ophthalmology, April 19 2016:

No evidence to suggest lasers pointed at cockpits damage pilots’ eyes
But at critical moments the dazzle and distraction could prove disastrous

There is no evidence to suggest that lasers pointed at airplane cockpits damage pilots’ eyesight. But obviously if directed at critical moments, the dazzle from the beam and ensuing distraction could prove disastrous for crew and passengers, say leading eye specialists in an editorial published online in the British Journal of Ophthalmology.

In a bid to disentangle the hype, amid the rising number of cases of laser pointers directed at aircraft—more than 1500 over the past 12 months in the UK alone—the specialists set out in which circumstances eyesight can be damaged.

There has only been one case of alleged retinal damage in a pilot as a result of laser targeting of aircraft, they say, and that is highly questionable because of the distances involved, which, crucially, would have reduced the energy entering the eye.

The nature and supply of current hand-held lasers have changed substantially in the past decade due to advances in technology and poor quality controls, so that the devices are considerably more powerful, write the authors. But they can only damage eyes at relatively short range up to several metres, they say.

Between half and one million laser pointers, pens, and key rings are thought to have been in circulation over the past decade.

But while these class 2 pointers on sale to the public predominantly used to produce red laser beams, with an upper limit of 1 milliwatt (mW) of energy—insufficient to damage the eyes—they now produce energy of up to 300 mW. These should be more appropriately classified as class 3B and prohibited from sale to the public, say the authors.

Furthermore, it is very easy to buy cheap laser pointers online with energy outputs of 1000 mW, while devices of up to 6000 mW are available for commercial use, they add.

These class 4 devices are capable of causing irreversible eye damage if directed into the eye from a distance of up to several metres. And some 150 children in the UK are thought to have lost their central field vision as a result.

But when directed to aircraft and helicopters over a long range—typically hundreds to thousands of metres—the beam has to pass through the atmosphere and the 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,” write the authors.

“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,” they write.

“Obviously, if such a distraction occurs at a critical time, such as during landing, the result could be devastating. Fortunately, these exposures are at irradiances that are incapable of producing irreversible retinal damage even at distances of 100 metres,” they continue.

Contrary to popular belief the current safety limits don’t need to be changed, say the authors. But the European Commission has asked the relevant European bodies to set a standard for consumer laser products.

"This should allow enforcing authorities to remove unsafe products from the market,” they write. But they warn: “However, compliance by manufacturers will remain an issue, as will direct imports by the public purchasing unsafe laser products over the internet.”