The recent flood of reports in the national press of the ocular dangers of laser pointers, sprinkled with claims of permanent eye injury, should provide an important reminder to industrial users to pay attention to a few of the basics of introducing laser technology:

• the hazards of lasers need to be properly explained to the work force;
• attention needs to be paid to the control of lasers in the work place, even low power lasers;
• the control of diode lasers in the work place requires particular vigilance;
• claims of laser eye injuries can arise even where only low power lasers are involved. Such claims need careful handling if litigation is to be avoided.

The laser pointers causing all the current problems are low cost imported visible (red, usually 670 nm) diode lasers with outputs up to 5 mW. Apart from their recreational uses, these lasers have serious industrial applications in sensing, monitoring and alignment.

Explaining the hazards.

The response of the general public and the news media is hardly surprising. The general perception of lasers even before the era of the low cost laser pointer was of a science fiction weapon, and surprisingly many people, though probably not those now causing all the problems with lasers pointers, still associate the dangers of lasers with the James Bond movie 'Goldfinger'. As with all areas of industrial safety, a proper explanation of the hazards and why and how imposed safety controls deal with the hazard, ensures maximum co-operation and minimum risk of litigation.

Users of Class 2 and visible 3A lasers should be made aware of the importance of the natural aversion response to bright light, the blink reflex, in preventing retinal injury. Believe it or not, the warning 'do not stare into the laser beam' which appears on these lasers is not always interpreted as 'do not attempt to resist the blink reflex'.

Control of lasers in the work place

The user guidance in EN60825-1 for Class 2 and 3A laser use has not changed for many years and is now in need of a complete overhaul. It talks about 'evaluating the hazard' and goes on to give some simplistic advice for different indoor and outdoor uses of lasers.

The guidance on the use of Class 2 and class 3A lasers in laboratory and workshop installations is not to intentionally aim the beam at people. However, a Class 2 laser pointer, for example, can seriously dazzle and distract and the consequences of such an occurrence during some laboratory and workshop activities can, of course, be serious.Without wishing to encourage an over-the-top response to the risk, it is important that supervisors assess the potential consequences of unanticipated dazzle. Where there is a risk of injury, control measures should be taken, even for Class 2 lasers use.

Control of diode lasers

Diode lasers are small (and therefore often unmarked), battery powered, easily mistaken for other semiconductor products and can (at least for a short time) be seriously overpowered. In all these respects, diode lasers present a unique laser safety problem. Of particular relevance to the laser pointer issue is the need for quality control to limiting the output of these devices to 1 mW, say, and to ensure that the diode assembly is properly labelled and, eventually, properly disposed of.

A recent random testing of laser pointers carried out by Dr Ajoy Kar of Heriot-Watt University in Edinburgh, found that many Class 3A laser pointers were operating over the stated maximum power; some as high as 15 mW! (This feature of excess output laser power is unique to diode lasers). One might expect that the more reputable suppliers of diode lasers for industrial use enforce tighter controls.

Another problem is the confusion between the American Class IIIA and the European Class 3A visible laser.

Dealing with suspected injuries

Years of animal experimentation indicates that the aversion response is sufficient to prevent visible CW lasers of up to 1 mW power from causing permanent injury and this is backed up by over 30 years of laser injury data. Indeed, it is generally accepted that at visible laser beams of at least 5 mW power are required to cause an injury through accidental exposure.

Use of laser pointers means that there have now been many recorded incidents of exposure. These often include reports of pain. The pain is most likely caused by the rapid contraction of certain eye muscles following sudden bright light exposure, and is not indicative of a permanent injury.

Nevertheless, there is many examples to show that people who experienced a bright laser 'flash' are likely to attribute the cause of any disorder subsequently discovered by the ophthalmologist, such as age-related degeneration of the retina or vascular disease, to the light exposure. This is to be expected, yet the result of such a work 'injury' can be time consuming and costly, especially for employers who, upon investigation, are found to have been negligent.

In the journal Ophthalmology (Volume 104, No 2, February 1997) a group of medical laser safety experts have addressed this issue. They point out that few ophthalmologists have experience of laser injuries and that such injuries are quite subtle and may be difficult or impossible to distinguish from other forms of retinal abnormality. The advice the authors give to ophthalmologists is not to jump to conclusions about a laser induced injury until an individual's light exposure history has been investigated thoroughly.

As one safety professional asked in a discussion on whether on not the sale to the general public of lasers over Class 1 should be prohibited, 'is a Class 2 laser any more dangerous than a box of matches?' The answer is clearly 'no', but unlike in the case of matches, today's general public has not grown up with an appreciation of safe laser use.

Pro Laser provides a complete laser safety service, including risk assessments, safety procedure drafting, safe system layout and design, laser classification, in-house training. Copies of the Ophthalmology editorial referred to above are available free of charge from Pro Laser.