British Journal of Ophthalmology, 1988, 72, 570-575

Retinal burns caused by exposure to MIG-weldingarcs: report of two cases

G P H BRITTAIN

SUMMARY A new generation of arc welder has recently become widely available at a price which iswithin reach of most amateurs and part-time mechanics, known as the MIG welder (metal-arc inertgas welder). In MIG welding the arc is ensheathed in a stream of inert gas which prevents themolten metal from oxidising. The stream of gas changes the character of the emitted radiation, andit is possible that this type of welder poses a greater threat to sight than previously recognised.Radiation in the ultraviolet range emitted by arc welders is absorbed by the unprotected cornea andlens, giving rise to a keratoconjunctivitis, or 'arc-eye,' which, though intensely painful, is notconsidered a threat to sight. Radiation in the visible and near infrared spectrum, however,penetrates the eye to be absorbed by the retina and may cause thermal or photochemical damagewhich may be permanent and sight-threatening. Retinal injuries resulting from exposure toordinary electric welding arcs have been reported, but such injuries are uncommon. Two cases ofretinal burns resulting from exposure to MIG welder emissions which presented on consecutivedays to the Leicester Royal Infirmary are presented. This is the first report of such injuries relatingspecifically to MIG welding.

The radiation emitted from electric welding arcs canextend across a wide spectrum from infrared toultraviolet and beyond.'2 Radiation in the ultravioletrange emitted by arc welders is absorbed by theunprotected cornea and lens, giving rise to kerato-conjuntivitis, 'welder's flash,' or 'arc-eye,' a conditionknown to welders and accepted as an occupationalhazard which, although intensely painful, is notconsidered a threat to sight in the long term. Butradiation in the visible and near infrared spectrum(400-1400 nm) penetrates the eye, to be absorbed bythe retina,3 where, given sufficient intensity andduration, it will cause thermal or photochemicaldamage` which may be permanent and sightthreatening. Retinal injuries resulting from exposureto welding arc radiation have been reported,79 butsuch injuries are uncommon.A new generation of arc welder has recently

become widely available at a price which is within thereach of most amateurs and part-time mechanics,known as the MIG welder (metal-arc inert gaswelder) or GMAW (gas metal arc welder) in theUSA. In MIG welding the arc is ensheathed in astream of inert gas which prevents the molten metal

Correspondence to Mr G P H Brittain FRCS, Department ofOphthalmology, Leicester Royal Infirmary, Leicester LEI 5WW.

from oxidising in air.2 The stream of inert gas changesthe character of the emitted radiation, and it ispossible that this type of welder poses a greater threatto sight than previously recognised.Two cases of retinal burns resulting from exposure

to MIG welder emissions which presented onconsecutive days to the Leicester Royal Infirmary arepresented. This is the first report of such injuriesrelating specifically to MIG welding.

Case reports

CASE 1A 26-year-old unemployed mechanic with no previousarc welding experience borrowed a MIG welder torepair the bodywork of his car. The protective visorwas not used because outside lighting conditionswere poor, making it difficult to see through the glassfilter. The patient estimated that he continued toweld intermittently over the course of one and a halfhours with no eye protection. The only attempt toprotect the eyes was made by 'looking away from thearc' and holding the welder at arm's length. The car'smild steel panels were welded with 0-6 mm copperedsteel wire to form the arc and Brewer's carbondioxide as the inert gas.

Later, in the dark, he became aware of a persistent570

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Retinal burns caused by exposure to MIG-welding arcs: report oftwo cases

Right Eye

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Fig. I Amslerrecordingchartsshowlngparacentralscotomas in rightand lejteyes.

bright spot near the centre of his vision. He presentedto his general practitioner and was referred on tohospital the following morning, still complaining of apositive scotoma affecting the lower part of his

central field in both eyes. This was plotted by thepatient on an Amsler grid at 30 cm (Fig. 1). A slightgritty sensation in both eyes was admitted to only ondirect questioning. Unaided visual acuity was

ig.2L mallaark lesionaboveeachfiovea. L:rignteye. 1: efteye.

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G PH Brittain

recorded as 6/5 in both eyes. Minimal, punctatecorneal fluorescein staining was seen on eacheye. Retinal examination revealed a triangular,oedematous lesion approximately 0-1 mm in size justabove and to the patient's left of each fovea (Fig. 2).One week later the patient's condition was

reviewed. At that time he was symptom free and theretinal lesions were no longer visible. Octopusperimetery (program 34) and fluorescein angiogramsof both fundi were normal.

CASE 2A 39-year-old Asian self-employed motor mechanicpresented to the hospital casualty department in theearly hours of the morning complaining of painful redeyes, photophobia, and blurred vision. The previousafternoon he had been welding a car body witha MIG welder. It was used underneath the car in poorlight, where it was not possible to see through thedarkened glass of the protective visor. The patientadmitted to 'occasionally' looking round the side ofthe visor 'for never more than a few seconds' until thearc was struck; enough light would then be producedto enable him to see through the glass filter and allowthe visor to be used in the correct manner. The inertgas used was a mixture of argon 75% and carbondioxide 25%. The arc was formed with 0-6 mmcoppered steel wire, and the car, body parts were ofmild steel. He was inexperienced at welding and hadused the machine five or six times, with a totalwelding time of less than five hours in the previous

seven months. He had never received any formalwelding training nor had he done any other arcwelding.He was treated with topical antibiotic drops and

eye padding. Seen in the eye department later thatmorning he complained of blurred vision and darkspots in both eyes; the eyes were still painful andphotophobic. His corrected visual acuity was 6/7 5 inthe right and 6/9 in the left eye. His conjunctivas werehyperaemic, and on slit-lamp examination bothcorneas showed fine, superficial, punctate fluoresceinstaining in the areas exposed by the palpebralfissures. Facial ultraviolet erythema was not noted.Examination of the fundi revealed two discretecircular brown coloured lesions in each eye. Thelesions were located rather symmetrically temporalto either fovea. The larger was over half a discdiameter in size, the other a third of a disc diameter insize in both eyes; each lesion contained a concentricring. The smaller lesion in the left eye was lessmarked than the other lesions (Fig. 3).One week later the patient was symptom free and

his corrected visual acuity had improved to 6/6 inboth eyes. Fundus fluorescein angiograms revealedhyperfluorescent areas in the early arterial phasewithout any leakage of fluorescein in later pictures(Fig. 4). These areas had the appearance of windowdefects in the pigment epithelium in locationscorresponding to the retinal lesions, and looked likethose found in retinal photocoagulation burns."' Novisual field defect could be located despite a careful

Fig. 3 Retinalburns In both eyes. L: rlghteye. K: ieJteye.

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Retinal burns caused by exposure to MIG-welding arcs: report oftwo cases

and detailed search with both tangent screenand computerised Octopus central field analyser(programs 34 and 64).

Discussion

Traditionally, the primary consideration of the ocularhazards of arc welding has been keratoconjunctivitiscaused by the ultraviolet radiation, which is producedin large amounts by the welding arc. Ultravioletradiation is absorbed by the cornea and lens3 andtherefore does not pose a threat to the retina in thephakic eye. However, arc welding emissions cover awide spectrum, much of which falls within the visiblerange.' The danger of excessive retinal exposure to'blue light' is well recognised.4 "The first case demonstrates a macular burn resulting

from prolonged exposure to the radiation of a carbondioxide MIG welding arc. Although a full recoverywas made, the injury was significant, for it shows thata sufficient proportion of the radiation produced bythe arc is within the spectral range that can reachthe retina to cause retinal injury. The lack of amarked keratoconjunctivitis despite the retinalinvolvement is of interest and may be explainedby spectral analysis of the carbon dioxide arcwhich produces relatively less radiation in theultraviolet range than in the visible and near infra-redspectrum (Fig. 5).12The macular burns in the second case, which

resulted from exposure to radiation from an argon

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arc, were symmetrically located temporal to thefovea. The principle of physiological diplopia'3 is wellillustrated, showing that the welding arc must havebeen closer to the eyes than the point of visualfixation (Fig. 6). As the intensity of light incident onthe retina is inversely proportional to the square ofthe distance of the source from the eye, this evidencethat the patient occasionally had his face very close tothe arc is a major factor in this retinal injury.'" 14

The total amount of radiation from an arc in anygiven period is approximately proportional to thesquare of the current and directly related to the arclength (or arc voltage). When using comparable non-professional equipment MIG welders operate atsimilar voltages but at almost twice the current of rod

Fig. 4 Pundusfluorescein angiograms c

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Argon Gas Emission Spectrum

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Fig. 7 Argon gas emission spectrum showing the relativeintensity ofthe majoremission bands.

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Fig. 6 Illustration oftheprincipleofphysiologicaldiplopia.F= fovea, X= weldingarc, B = retinalburn, 0 =fixationobject.

arc welders. Whereas a welding rod is of some 2 mmin diameter and produces an arc about 2 5 mm in

diameter, the MIG uses a wire 0-6 mm in diameterproducing an arc less than 1 mm in diameter. Atsimilar operating currents a MIG produces a currentdensity six times higher (or six times brighter) than a

rod arc. MIG welding differs from standard rod arc

welding in that the molten metal is protected fromoxidation in air by a stream of inert gas rather than bya melted flux. Radiation from a MIG welding arc isnot blocked by the surrounding fumes and the moltenslag in which a conventional rod arc is submerged.The MIG welding arc is produced by direct current,and its emissions are continuous. A traditional rodarc is driven by an alternating current and so theemissions are pulsed and interrupted, reducing thetotal exposure for a given period. These factorsmean that a MIG arc is many times more intensethan a conventional arc (Salter GR, personalcommunication).The stream of inert gas in a MIG welder allows a

controlled, steady arc to be formed. Since every

substance has its characteristic ionisation emissionspectra, introducing an inert gas to an electric arc willchange the spectrum accordingly. When argon is

excited by an electrical discharge, the majority of itsmost intense spectral bands fall within the visible andnear infrared range" (Fig. 7). The combined emissionspectra of argon and carbon dioxide from the gas mixused by MIG welding machines is maximal across thevisible spectrum. ' Such light freely traverses theocular media (Fig. 8) to be absorbed by the retinal

pigment epithelium and choroid' "''l - the basis ofargon laser retinal therapy.

Time-resolved optical spectra from 200 amp MIGwelding arc ignitions have been analysed'6 and showthat there is surge of radiation in the ultraviolet andblue light range that occurs within the first 50milliseconds of the arc being struck. The wave lengthof the emitted radiation is inversely proportional tothe current driving the arc2 (Salter GR, personalcommunication) and it is likely that, at the lowercurrents at which amateur MIG welding machinesoperate (below 100A), more of the emission will beof a longer wavelength and able to reach the retinaduring this initial surge on striking the arc.

The filter recommended by the British StandardsProtection of Eyes Regulations 1974 for MIG weldingis considerably darker than that recommended forrod arc welding, making it more difficult to see

through before the arc is struck. The temptation forthe inexperienced welder to look round the visor to see

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Fig. 8 Percentage emission through ocularmedia. Spectraltransmission curve ofocularmedia (after GeeraetsandBerry').

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Retinal burns caused by exposure to MIG-welding arcs: report oftwo cases

where the arc will ignite is understandable, especiallyin poor background lighting conditions where itis impossible to see through the visor. In theseconditions pupils would be dilated, allowing a muchhigher part of the incident light to be focused on theretina. The amount of light falling on the retina isproportional to the square of the pupillary diameter. "

Pupillary constriction in response to striking the arc istoo slow to block the initial 50 ms surge of radiation.

Safety advice given with amateur welding equip-ment does not adequately stress the risk ofnot wearingeye protection at all times, the importance of goodbackground lighting, or the danger of welding tooclose to the eyes.'7MIG welding machines were at one time expensive

and accessible only to the trained professional. In thepast few years they have become readily available at aprice within easy reach of the average amateur. Theycan be worked from a standard 13 amp domesticelectricity power supply, and, unlike standard arcwelding techniques, MIG welding requires very littleskill to use and is ideally suited for welding the thinsheet metal on cars. 17The intensity and spectrum of radiation of MIG

welders differ from those of standard rod arc weldersand may present a more serious risk to sight inthe unprotected eye than previously recognised,especially in the inexperienced hands of the amateur.It is likely that in future, with the increasing popularityof MIG welding machines, their misuse will give riseto many more cases of macular burns.

I am greatly indebted to Dr George R Salter, of the Welding Institute,Abington, Cambridge, for his help in supplying much of the technicalinformation.

References

1 Naidoff MA, Sliney DH. Retinal injury from a welding arc. AmJOphthalmol 1974; 77: 663-8.

2 Koenigsberger F, Adair JR. Welding technology 3rd ed. London:Macmillan, 1965.

3 Geeraets WJ, Berry ER. Ocular spectral characteristics as relatedto hazards from lasers and other sources. AmJ Ophthalmol 1968;66: 15-20.

4 Mainster MA, Ham WT, Delori FC. Potential retinal hazards.Ophthalmology 1983; 90: 927.

5 McDonald HR, Irvine AR. Light-induced maculopathy from theoperating microscope in extracapsular cateract extraction andintraocular lens implantation. Ophthalmology 1983; 90: 945-51.

6 Robertson DM, Feldman RB. Photic retinopathy from theoperating room microscope. Am J Ophthalmol 1985; 101: 561-9.

7 Uniat L, Olk RJ, Hanish SJ. Arc welding maculopathy. Am JOphthalmol 1986; 102: 394-5.

8 Minton JH. Occupational diseases of the lens and retina. BrMedJ1949; i: 392.

9 Wurdemann HV. The formation of a hole in the macula. Lightburn from exposure to electric welding. Am J Ophthalmol 1936;19:457.

10 Zweng HC, Flocks M, Peabody R. Histology of human ocularlaser coagulation. Arch Ophthalmol 1966; 76: 11-5.

11 Sliney DH. Eye protective techniques for bright light. Ophthal-mology. 1983; 90: 937-44.

12 Inoue K. Image processing for on-line detection of weldingprocess (Report III) - improvement of image quality by incorpor-ation of arc. Transactions of the Japanese Welding ResearchInstitute. 1981; 10: 13-8.

13 Roper-Hall G, Burde RM. In: Moses RA, ed. Adler's physiologyof the eye. St Louis: 1981; 7: 175.

14 Sliney DH, Freasier BC. Evaluation of optical radiation hazards.Apple Optics 1973; 12: 1-24.

15 Striganov AR, Sventitskii NS. Tableofspectral lines ofneutralandionised atoms. Atomic spectroscopy laboratory IV Kurchatovlaboratory of atomic energy. New York: IFI/Plenum Press, 1968.

16 Eriksen P. Time resolved optical spectra from MIG welding arcignitions. Am Ind Hyg Assoc J 1985; 46: 101-4.

17 Porter L. MIG weldingstep bystep. SIP (Industrial Products) Ltd,Loughborough: 1984.

Accepted for publication 28 April 1988.

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