ORIGINAL ARTICLE

H. Moseley � F. M. Tulley � C. N. J. McGhee

The potential hazard of laser pointers

Received: 1 March 2002 /Accepted: 5 July 2002� 2003 Springer-Verlag London Limited

Abstract We have examined 30 laser pointers that havebeen removed from the possession of accused persons bypolice in Scotland. An analysis has shown that 28 wereClass 3B (European), with radiated power up to9.3 mW. We have reviewed the relevance of these find-ings and this shows that they are potentially hazardous ifviewed directly. Transient exposure is unlikely to causelong-term damage but prolonged exposure may causepermanent retinal injury. They may also cause dazzle,the consequences of which could be serious.

Keywords Laser pen � Laser pointer � Risk assessment

Introduction

Laser pointers were intitially introduced as a lecturingaid. However, as the cost of production of these devicesfell, a new market opened up as a novelty item. Theywere sold as laser pens or keychains costing approxi-mately 20 Euros. The laser device (Fig. 1) is small – itmay be fitted in the palm of the hand – and is poweredfrom small button-size alkaline batteries. Children andteenagers in particular have obtained these deviceswithout any regard to possible safety implications.Consequently, there has been widespread concern

regarding the possible dangers posed by inappropriateuse of laser pointers. This has been fuelled by reports inthe media about ‘blinding’ effects and ‘intense pain’experienced by those who have been deliberatelyexposed to light from these devices. Victims haveincluded soccer players, as well as drivers of police carsand fire appliances.

There is a laser product classification scheme which isintended to provide some degree of protection to thepublic. Unfortunately, there is scope for some confusionbecause of a subtle but important difference betweenAmerican [1] and European [2] standards.

In Europe, laser classification as outlined by the In-ternational Electrotechnical Committee (IEC) applies[1]. The relevant part is the definition of Class 3A and 3Bdevices. With regard to laser pointers the relevantwavelength region is between 400 and 700 nm. In thisspectral region, for exposure times greater than 0.25 slimits on accessible emission levels (AELs) for Class 3Aare twofold: (1) radiated power must not exceed 5 mW;(2) irradiance limit is 25 Wm)2 averaged over a pupildiameter of 7 mm. This latter condition is equivalent to1 mW of radiated power entering the pupil of the eye. Ifthe beam diameter is 7 mm or less (as is the case in mostlaser pointers) then the power limit for this class is ef-fectively 1 mW. Radiated power may be greater than1 mW provided the beam diameter is greater than 7 mm.At the limit of 5 mW the beam diameter must be at least16 mm. Otherwise the device is Class 3B. The AEL forClass 3B is 0.5 W.

In the USA the classification set down by theAmerican National Standards Institute (ANSI) applies[2]. This differs from the European standard in oneimportant respect, namely the AEL for Class IIIA issimply a power limit of 5 mW; there is no 25 Wm)2

irradiance limit. So, a laser may be Class IIIA by theAmerican standard and Class 3B in Europe. In thecase of laser pointers, this region of confusion appliesto lasers emitting power between 1 and 5 mW.

A study reported previously [3] showed that 78%of laser pens examined on sale in Edinburgh were

Lasers Med Sci (2003) 18: 63–67DOI 10.1007/s10103-002-0245-3

H. Moseley (&)The Photobiology Unit, University of Dundee,Ninewells Hospital & Medical School,Dundee DD1 9SY, Scotlande-mail: H.Moseley@dundee.ac.uk

H. Moseley � F. M. TulleyDepartment of Medical Physics, University of Dundee,Ninewells Hospital & Medical School,Dundee DD1 9SY, Scotland

C. N. J. McGheeDiscipline of Ophthalmology,University of Auckland, Auckland, New Zealand

actually Class 3B devices. Subsequently, the authorspresented a preliminary risk assessment pertaining tolaser pointers [4]. In the present paper the authorspresent their results from a study of 30 laser pointersremoved from accused persons by police in Scotland.The laser pointers discussed in this paper were allremoved from persons who were allegedly using themin a reckless manner. Since they are the subject ofprosecutions it is not appropriate to consider thisaspect in any specific case.

Materials and methods

Thirty devices taken from possession of accused persons by policein Scotland were examined between December 1997 and March2000. Radiated emission was measured at a distance of150 ± 5 mm using a calibrated Ophir PD200 laser power meter.An average of three readings was determined. Measurements weretaken both with existing batteries and with new batteries. Beamdiameter was measured at exit aperture, 150 ± 5 mm, and at2.0 ± 0.1 m. In twenty cases wavelength was measured using acalibrated double grating Bentham spectroradiometer.

Issue 2 1997 of EN 60825 states that the minimum distance ofthe measurement aperture shall not be less than 100 mm from theapparent source. When a source is viewed at close distance it be-comes an extended source and the image on the retina is spreadover a larger area. For a laser pointer, typically, the transitiondistance from point source to extended source is approximately125 mm. Accordingly, irradiance through 7 mm aperture at150 mm was used for classification. Since the beam diameter wasless than 7 mm both at source and at 150 mm, this did not affectthe classification.

Devices were classified according to the European classification[2].

Results

The results are summarised in Table 1.Of the 30 devices 28 were classified as Class 3B

according to the European classification scheme. In thecase of item number 16, this had a detachable end-piece

which produced a pattern. The higher reading refers tothe end-piece removed.

The devices all emitted red light.Three devices had power outputs greater than 5 mW,

which would be classified Class IIIB by the Americanstandard. The others (except for item 21 which was aClass 1 LED and not a laser diode) would all be ClassIIIA by the American standard. The highest powermeasured was 9.3mW. The highest irradiance through a7 mm limiting aperture was 242 W/m2, which is almost10 times greater than the European maximum for aClass 3A laser.

Labelling on most devices was either inaccurate ornon-existent.

Discussion

There has been some scientific debate regarding thesafety of laser pointers [4,5]. Of 30 lasers seized by policein Scotland on grounds of alleged reckless use andexamined in this study 28 were Class 3B devicesaccording to EN 60825. Furthermore, this standardstates in section 9.2 Description of laser class ‘Class 3B:Direct intrabeam viewing of these lasers is alwayshazardous’. For reasons outlined below, it seemsreasonable to the authors to describe these lasers as‘potentially hazardous’.

In the first place, it is useful to consider any situa-tion where subjects have been exposed to similar powerlevels. An example of this is retinal photocoagulation.During this procedure, an aiming beam of approxi-mately 1 mW or less is directed on to the retina priorto firing the main beam. Until the mid 1990s, the usualpractice was to use an attenuated version of the mainargon beam, comprising 488 and 515 nm lines. A seriesof studies carried out on ophthalmologists showed thatthere was a reduction in colour discrimination amongargon laser users [6]. It was thought that this was due

Fig. 1 Example of a laserpointer

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to prolonged exposure to the blue component in theaiming beam. Since then, ophthalmic lasers have beensold using a red aiming beam with no reported ill-effects. This is of course a very different pattern ofexposure from that which may occur with laser point-ers since the ophthalmologists were exposed to verylow levels over a prolonged period. As regards effectson patients there is no evidence that a 1 mW redaiming beam has inflicted any damage. However, per-manent lesions can be produced by focusing a kryptonlaser beam (647 nm) of 100 mW or less for 0.1 s on toa 100 lm spot on the retina.

The normal aversion response (including blink reflex)would be expected to prevent retinal damage at thesepower levels. This is usually considered to act within0.25 s. However, recent work suggests that the blinkreflex may not exist for low power lasers [7]. Out of 48volunteers tested with red laser light, none exhibited ablink reflex for an exposure lasting 250 ms. In contrastto illumination using a conventional light source, laserirradiation only lights up a small area of the retina andthis may not be sufficient to trigger the response. Thesestudies were conducted at up to 1 mW and it is notknown whether these findings would apply at higher(e.g. 5 mW) powers. Also, in these experiments subjectswere aware that a laser light was going to be shone intotheir eyes. However, there are grounds for uncertainty as

to the validity of the assumption of a blink reflex con-ferring protection in these cases.

Victims who have been exposed to a laser pointeroften complain of a painful red eye. Direct ocularexposure might well cause transient disruption of nor-mal vision, which may be very distressing to the victim.Also, it would be a natural reaction to rub the eye whichmight induce further irritation and discomfort. This mayproduce pain if the cornea is inadvertently scratched orsuffers abrasion that leads to a red eye. So, we wouldassert that the exposure to the low power laser beamdoes not cause pain directly, but it induces a course ofevents which may lead to an uncomfortable or painfuleye. In our experience, the individual may be quite dis-tressed because of fear that sight may be permanentlydamaged.

There is an additional risk as a result of dazzle.Clearly the hazard depends on the nature of the activity.In some cases, police officers and fire crew have statedthat the laser beam struck their eye while they weredriving and this could have serious consequences. Lundet al. [8] conducted experiments with army volunteers.They concluded that, in a dark environment, significantflash blindness could be generated by a 1 mW laserpointer at 10 m and even at 100 m could cause enoughglare to disable a driver’s vision. So, if the laser pointerwere shone at the eyes of someone who was driving then

Table 1 Results from devicesremoved from accused persons Power (mW) Irradiance

at 150 mm(W/m2)

Average irradianceat 150 mm over7 mm (W/m2)

Wavelength(nm)

Classification

1 4.9 698 128 3B2 3.3 260 85 3B3 2.5 421 65 3B4 2.8 391 72 3B5 5.8 1857 152 3B6 1.7 44 3B7 3.0 308 77 3B8 2.8 291 73 3B9 1.1 156 29 3B10 2.6 270 68 3B11 4.6 937 120 654 3B12 4.0 1273 104 654 3B13 3.3 1040 85 661 3B14 1.7 236 43 662 3B15 3.6 512 94 657 3B16a 2.1 217 54 658 3B16b 3.4 356 89 658 3B17 2.3 186 61 655 3B18 2.8 221 72 659 3B19 2.5 258 64 648 3B20 9.3 1316 242 660 3B21 <0.1 657 122 4.1 577 106 653 3B23 3.4 693 88 655 3B24 0.5 109 14 649 225 2.3 318 58 652 3B26 6.0 849 156 662 3B27 2.5 256 64 646 3B28 2.3 475 61 649 3B29 4.8 672 124 656 3B30 2.2 317 58 654 3B

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this might well dazzle the driver and this could of coursebe dangerous.

Another problem with the widespread availability ofthese lasers is that they are being purchased by children.A new version of the traditional children’s game of‘chicken’ had developed in relation to these new ‘toys’,the game of ‘chicken’ being won by the child whocould stare directly into the laser beam for the longestperiod.

A report was published by the Dundee group in 1998[4] on the potential risk of eye injury from the inap-propriate use of laser pens. However, Marshall [5]reached a very different conclusion, namely that ‘laserpointers, pens, or key rings if used appropriately are notan eye hazard, and even if used inappropriately will notcause permanent eye damage’. It goes without sayingthat we would agree that a laser pointer used appro-priately is not an eye hazard. However, the reality is thatit is extremely unlikely that in the hands of the generalpublic they will at all times be used appropriately. Thesecond point is whether such devices even if used inap-propriately will cause permanent eye damage. A recentincident, described below, supports the cautionexpressed by the Dundee group [9].

An article published by Luttrull and Hallisey [10] is ofsignificant importance to anyone dealing with casesrelating to laser pen exposure. The reported case in-volves a 34-year-old male who deliberately stared intothe beam of a Class IIIA (American) laser held 8–10inches (20–25 cm) from the eye for 30–60 s. Accordingto the label, the laser had a power less than 5 mW at awavelength of 670 nm. The patient reported a transientvisual field loss (central scotoma) and headache afterexposure. On examination 2 days later, a focal retinalpigment epithelial disturbance was evident at the nasaledge of the fovea in the left eye which led the authors toconclude that ‘laser-pointing devices may cause macularinjury when used inappropriately’. Another case wasreported in which macular damage was caused by star-ing at a laser pointer for a duration allegedly of the orderof 10 s [11]. Within 8 weeks, the patient’s visual acuityand visual field returned to normal but a retinal pigmentepithelial abnormality persisted.

It should be noted that most reported cases ofexposure to the laser beam appear not to result in per-manent ocular injury. A follow-up of 14 cases whoattended casualty in Bristol following transient laserexposure has been published [12]. The commonestphysical sign was a punctate epitheliopathy of the cor-nea, seen in 5/14 cases, and the commonest symptomwas discomfort, reported by 11/14 patients. However,after a mean interval of 10.5 months following exposure,the study failed to demonstrate consistent, long-termdamaging effects. A review among Dutch ophthalmol-ogists up to June 1998 revealed no cases of permanentdamage caused by laser pointers [13]. Although thissupports the view that the risk is minimal, the authorsconsider it advisable to prohibit the sale of laser pointersemitting more than 1 mW of light.

In one study three human eyes containing uvealmelanomas were exposed to light from a laser pointerprior to enucleation [14]. Three laser devices of outputs1, 2 and 5 mW were used (wavelength 659 and 673 nm)for exposure duration of 15 min. The 2 and the 5 mWpointers produced a pink after-image which lasted for afew minutes. However, the investigators found no evi-dence of either acute laser injuries nor delayed photicretinopathy. This investigation shows that it is veryunlikely that transient exposure to a laser pointer wouldcause serious retinal injury.

New classification standards are under discussion.They are mainly directed towards introducing a relax-ation of highly divergent devices, such as LEDs. Productswhich would be Class 1 or Class 2 except by viewing byoptical aids, will become Class 1M or 2M, respectively.Class 2M will have an AEL of 1 mW. A new Class 3Rwill have an AEL of 5 mW for visible. Class 3B will havean AEL of 0.5 W for visible, as at present. The questionarises as to how the lasers in the present investigation willbe classified under the new scheme. Those which aremore than 5 mWwill be Class 3B as at present. However,those which are between 1 mW and 5 mW will becomeClass 3R because the 25 Wm)2 criterion no longerapplies. This means that those devices which were Class3B according to both American and European standardswill still be Class 3B. However, those which were ClassIIIA (American) but Class 3B (European) will becomeClass 3R. This effectively downgrades most of the devicesfound to be Class 3B in the present investigation. Itshould be noted that the authors described these laserpointers as being ‘potentially hazardous’ in an earlier riskassessment and these words are exactly the same as usedin the new standard to describe a Class 3R device. So ouroriginal assessment still holds. Moreover, the maximumpermissible exposure (MPE) for direct viewing a visibleradiation laser for duration 0.25 s is still unchanged at25 Wm)2 through a limiting aperture of 7 mm (theassumed size of the pupil). This diameter corresponds tothat of a fully dilated pupil and is used as a worst casescenario for risk assessment. This irradiance is equivalentto a power of 1 mW averaged over a 7 mm diameterarea. In other words, shining a Class 3R laser pointer ofpower greater than 1 mW into someone’s eye exposesthat person to irradiation which exceeds the MPE value.Under conditions of good illumination, e.g. bright sun-light, the pupil diameter will be smaller and this willafford protection from a large area beam, but this cannotalways be guaranteed to be the case when a laser pointeris misdirected. So, all the devices designated Class 3B inthe present study are potentially hazardous since theyare capable of exposing the eye to an irradiance whichexceeds the maximum permissible exposure level.

Conclusions

1. Many laser pointers in the hands of the general publicare Class 3B lasers (European).

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2. Transient exposure may induce an after-image for afew minutes but is unlikely to cause long-term oculardamage.

3. Retinal change may occur after deliberate exposurefor periods of the order of 30–60 s.

4. Additional discomfort may result from rubbing theeye.

5. There is an additional risk of dazzle which could beextremely serious if engaged in a critical activity.

6. Our conclusion is that exposure to the beam ispotentially hazardous.

References

1. ANSI Z136.1 American National Standards Institute (1993)Safe Use of Lasers

2. EN 60825-1 British Standards Institution (1997) Safety ofLaser Products

3. Moseley H, Tulley FM (2001) Assessment of the risk fromlaser pointers. Proc SPIE Clinical Lasers Diagnostics 4156:137–141

4. McGhee CNJ, Craig JP, Moseley H, Keller P (1998) Laserkeychains; potential for serious injury. Eye News 4: 17–19

5. Marshall J (1998) The safety of laser pointers: myths andrealities. Br J Ophthalmol 82: 1335–1338

6. Arden GB, Berninger T, Hogg CR, Perry S (1991) A survey ofcolor discrimination in German ophthalmologists. Changesassociated with the use of lasers and operating microscopes.Ophthalmology 98: 567–575

7. Raidenbach HD (2001) Blink study demands a closer look.Opto-Laser Europe September pp 13

8. Lund DJ, Stamper DA, Molchany JW, Stuck BE (1999)Transient visual effects. Proc Int Laser Safety Conf 4: 73–82

9. McGhee CN, Craig JP, Moseley H (2000) Laser pointers cancause permanent injury if used inappropriately. Br J Ophthal-mol 84: 229–230

10. Luttrell JK, Hallisey J (1999) Laser-pointer-induced macularinjury. Am J Ophthalmol. 127: 95–96

11. Zamir E, Kaiserman I, Chowers I (1999) Laser pointer mac-ulopathy. Am J Ophthalmol 127: 728–729

12. Sethi CS, Grey RH, Hart CD (1999) Laser pointers revisited: asurvey of 14 patients attending casualty at the Bristol EyeHospital. Br J Ophthalmol 83: 1164–1167

13. van Norren D, Keunen JE, Vos JJ (1998) The laser pointer: nodemonstrated danger to the eyes. Ned Tijdschr Geneeskd 142:1979–1982

14. Robertson DM, Lim TH, Salomao DR, Link TP, Rowe RL,McLaren JW (2000) Laser pointers and the human eye: aclinicopathologic study. Arch Ophthalmol 118: 1686–1691

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