Brit. J. Ophthal. (1976) 6o, 632

Cataract after exposure to non-ionizing radiant energy

MILTON M. ZARET, WENDY Z. SNYDER, AND LEO BIRENBAUMFrom New York University Medical Center, Departments of Ophthalmology and Physiology, andPolytechnic Institute of New York, Department of Electrical Engineering and Electrophysics

The case reports that follow suggest that infraredradiation emitted from an electric oven and stovecould be a contributory or aetiological factor in thedifferential diagnosis of cataracts.During the past 30 years, there has been a constant

increase in the number of devices such as diathermymachines, microwave ovens, and electric stoveswhich emit radiant energy. While industrial heat(infrared) cataract in glassblowers and furnaceworkers was first recognized nearly 200 years ago(Wenzel, I786), lens damage caused by microwaveirradiation is a disease related to modern technology(Daily, Wakim, Herrick, Parkhill, and Benedict,I952; Richardson, Lomax, Nichols, and Green,1952; Shimkovich and Shilyaev, i959; Zaret, i964;Bouchat and Marsol, I967; Kurz and Einaugler,I968; Zaret, I974a, b). In both types of cataractthe aetiology of the lesion has usually been explainedin terms of thermal damage from absorbed radiation.In view of the long latent period often observedbetween exposure to repeated, subliminal doses ofinfrared or microwave radiation and the appearanceof clinical cataracts, it has been suggested (Duke-Elder, 1972a) that single exposures to such radiations,which are not of themselves harmful, may becomehazardous if repeated sufficiently often. Further-more, the shorter the interval between subthresholdirradiations, the more likely it becomes that suchlens changes ultimately will develop.

In this paper we present two case reports, that ofa wife and husband, with different histories ofexposure to non-ionizing radiant energy. Eachindividual developed a specific type of ocular lesionrelatable to exposure. The woman, who receivedmedical diathermy treatment for a back injury and,in later years, cooked on an electric oven and range,developed capsular cataracts in both eyes; thedelayed type of cataractogenesis after diathermytherapy, instead of remaining latent, appeared tobe exacerbated and hastened by additional exposureto infrared emission from the cooking device. Herhusband, who had a longer history of exposure tothe electric range only, developed first a retinopathyand later a lens capsule opacity both resemblinginjury from non-ionizing radiation. Clinical and

Address for reprints: Milton M. Zaret, MD, 1230 Post Road,Scarsdale, New York 1oS83, USA

histological evaluation of the cataractogenesis andcapsulopathy will be discussed.

Case reports

CASE I

This 46-year-old White woman was first examinedon 4 January 1975, having been referred because ofunusual cataracts. During the previous two years, hereyeglasses had been changed at approximately three-monthly intervals because of changes in refractive errorand an intermittent esotropia. Visual acuity was cor-rectable to 20/20 minus for the right eye and 20/30 minusfor the left eye; her only complaint regarding clarity ofvision was that it appeared as if she were lookingthrough a transparent curtain with her left eye.

Slit-lamp examination revealed a large, irregularlyoutlined, honeycombed capsulopathy involving morethan half of the posterior surface of the lens. A few regionsof vesiculation and opacification were present in the lenssubstance at its interface with the capsule. Thus, all ofthe disease was limited to the posterior lens capsule andadjacent, contiguous surfaces of the lens substance.This form of capsular cataract was present bilaterally,being slightly more extensive in the left than the rightlens. Fig. I is a photograph of the left eye taken at thetime of this examination.There was nothing in the patient's history to suggest

an aetiology except exposure to a course of medicaldiathermy as therapy for back pain approximately I5years earlier.The diagnosis was incipient, delayed radiant energy

cataract. The patient was advised that this type of cataractordinarily would lie dormant or progress very slowlyover a time period measured in years, that no treatmentother than surgery was available, that surgery was notindicated at this time, and that she should avoid anyadditional exposure to radiant energy, especially non-ionizing radiation such as from medical diathermy ormicrowave ovens. She was instructed to return for afollow-up examination after an interval of three to sixmonths because no significant changes were expected tooccur sooner.However, within two months the patient had observed

both a further decrease in vision which now madedriving at night hazardous and increased difficulty inreading because the esotropia recurred more frequently.Therefore, she returned for re-examination on 15 March.At this time the best correctable visual acuity of theleft eye was reduced to 20/40 minus due to progressionof the cataractous changes. It was also noted that after

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Cataract after exposure 633

FIG. i Lens photcgraph, Case i, left eye. Note cataractformation limited to posterior surface of lens

instillation of mydriatics the pupils did not dilate well;this is not an uncommon, late finding in non-ionizingradiation cataracts, occasionally indicating the formationof posterior synechiae located peripherally, at the pointwhere the iris first lies in apposition with the anteriorbulge of the lens. This suspicion of synechiae was con-firmed at cataract surgery performed on I 5 April, whenit was necessary to perform posterior synechiotomiesto free the lens from iridial adhesions in order to extractthe cataract without rupturing the lens capsule.By 9 August 1975, the cataractous process in the right

eye had also become more extensive, the lesion nowinvolved most of the posterior surface of the lens and,in addition, a marked capsulopathy had become evidentat its anterior surface. The patient's complaints werehazy vision and intermittent diplopia. Visual acuity wasreduced to 20/50 plus or minus.

Cataract extraction was performed on the right eyeon 20 August. At surgery, the anterior capsule wasfound to be adherent to the iris and the posterior capsulewas adherent to the face of the vitreous. The adhesionswere lysed and the lens was then delivered from the eyeintracapsularly. After surgery, visual acuity was correct-able to 20/20 plus in each eye separately and the resultantrestoration of the ability for fusion corrected the inter-mittent esotropia.

In view of the unusually rapid development of thispatient's cataracts, which took place over a period ofmonths rather than years, an investigation was under-taken to determine whether some additional radiantenergy source in the patient's environment could havebeen providing repeated, covert exposures, thus beinga contributory factor. The only suspicious element wasthat, since her marriage on 8 December 1973, she hadused an electric range and oven. Both she and herhusband worked and, as he ietumed home earlier thanshe, frequently he would cook the dinner. For thisreason, it was decided to examine his eyes for signs ofradiant energy effects.

CASE 2

This asymptomatic 55-year-old man was firstexamined on 3 May I975. His medical and occupationalhistories were negative regarding serious illness orsignificant exposure to non-ionizing radiation.The examination findings were physiological except

for ophthalmoscopy. In the left eye, the macula exhibitedpigmentary changes, generalized hyperpigmentationwith a few scattered minute areas of depigmentation, afinding seen rarely in general population groups but notinfrequently in workers where the occupational environ-ment has an increased ambiance of photic energy(infrared and high intensity light environments) (Duke-Elder, 1972b; Zaret, 1972). Also in the left eye, a smallarea of pigmentary, degenerative change was presentsuperiorly between the macula and optic disc. Thesechanges are shown in Fig. 2, a retinal photograph ofthe left eye. In the right eye, two minute areas ofdepigmentation, each about o-I mm in diameter, werefound in the inferior region of the macula. By slit-lampexamination, both lenses were entirely physiological.

After an interval of six months, the patient was re-examined on 22 November I975. His visual acuity hadremained correctable to 20/20 in each eye. However,the maculopathy had become more marked in both eyes.More importantly, by slit-lamp biomicroscopy a smallarea of capsular opacification measuring about i -o mmin largest diameter had now become apparent at theposterior sturface of the left lens. These retinal and lensfindings are compatible with frequently repeated ex-posure to non-ionizing radiation.

In view of the implication that the electric oven andrange could have served as a harmful, covert source ofradiant energy exposure for both patients, beingcontributory to Case I and causal for Case 2, measure-ments were made of its emissions.

FIG. 2 Retinal photograph, Case 2, left eye. Notepigmentary degenerative changes

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634 British Journal of Ophthalmology

MEASUREMENTS OF ELECTRIC OVEN AND RANGEEMISSION

Measurement of the radiant energy emission wasaccomplished by using a calibrated Eppley thermopileand a Keithley model IsoB microvolt ammeter.

Irradiation measurements of the electric oven withthe controls set at the 'broil' position were taken at a

distance of 30-4 cm in front of the door. The values were24 mW/cm2 with the door closed and 97 mW/cm2 withthe door open.The electric range had four bumers, two in front and

two at the back. Measurements were taken at a distanceof 45-7 cm in front of the range. With one front bumeron 'high', the irradiation flux was 57 mW/cm2. With one

front and the ipsilateral rear bumer on 'high', themeasured emission was 97 mW/cm2. No measurementswere made with all of the stove sources emitting, as

such a flux of radiant energy would have exceeded byfar the solar constant, an obviously hazardous conditionfor direct exposure of the eyes.

ResultsHISTOLOGICAL FINDINGS

After cataract extraction the right lens was im-mediately placed in 4 per cent glutaraldehydebuffered with O-I mol/l sodium cacocdylate for I20hours at room temperature (approximately 24°C).The tissue was rinsed in buffer with 4 per centsucrose, sliced into anterior and posterior segmentsand postfixed for four hours in I per cent osmiumtetroxide buffered with the cacocdylate-sucrosemedium. After further rinsing in buffer anddehydration in a graded series of alcohols, thetissue was trimmed and cut into small strips andembedded in epon. Thick (I to 2 ,Lm) sections were

cut on a Porter-Blum (M-2) ultra-microtome,stained with i per cent methylene blue and photo-graphed under oil (X 56o) with a Zeiss photomicro-scope.

Fig. 3 shows the anterior surface of the lenslying behind the iris. Note the posterior synechiaewith pigmented precipitates deposited on theanterior lens capsule. The subcapsular epitheliumappears vacuolated and several cell nuclei seem

pyknotic. In Fig. 4 a more central area of theanterior surface of the lens is shown. Here, the non-

uniform staining of the capsule is apparent and thesubcapsular epithelium is vacuolated.

Figs 5 and 6 represent the posterior surface ofthe lens. In Fig. 5 note the irregular, outer surfaceof the posterior capsule and the vacuolization ofthe posterior cortex. The splitting of the capsulefrom the subcapsular cortex is an artefact. Fig. 6shows the non-uniform staining of the posteriorcapsule. There appears to be a large area of sub-capsular degeneration of the cortex as well as

vacuolization of discrete areas. A close inspectionof the inner surface of the capsule reveals that lens

substance is adherent to it, thus obliterating thepotential subcapsular space. Another feature ofthis apparent adhesion of the lens substance tocapsule is that the lens substance at this site is moredensely stained. Perhaps this may explain theearliest clinical appearance by slit-lamp bio-microscopy of capsulopathy in non-ionizing radia-tion cataract.

Discussion

The clinical findings and course for Case i suggestthat the earlier exposure to medical diathermyradiation produced a covert, slowly progressing,pathological process which was later accelerated byrepeated exposure to infrared radiation. Otherwise,there was an unusually short duration of timerequired for the full evolution of the non-ionizingradiation cataracts.The histological appearance of the cataractous

lens includes features previously described inexperimental and clinical lesions produced afterrepeated, subliminal exposure to infrared or micro-wave irradiation. The pathological findings of theanterior surface of the lens-including pigmentdeposition on the anterior capsule, swelling andvacuolization of the subcapsular epithelium, andneighbouring lens fibres in association withposterior subcapsular vacuolization-are typical ofof an infrared lesion (Vogt, 1930; Goldmann, 1932;Langley, Mortimer, and McCulloch, I960). Vesicu-lation or honeycomb appearance at the posteriorcapsule and subcapsular cortex is more characteristicof medical diathermy or microwave-induced cata-racts (Zaret, I964; Bouchat and Marsol, I967;Kurz and Einaugler, I968; Zaret, I974a and b).This patient exhibited both infrared and diathermyradiation findings. Thus it appears that thehistological evaluation of the lens supports theclinical impression that the more recent infraredexposure was effective quickly because of earlierexposure from medical diathermy.The pathogenic cause of non-ionizing radiant

energy cataract is probably not as simple as someinvestigators have implied. For example, infraredrays are reported to be absorbed mainly by thepigment epithelium of the iris (Goldmann, 1932;Langley and others, I960), and converted to heatwhich may damage the adjacent capsule andsubcapsular epithelium of the lens. Local increasein temperature at the anterior surface of the lens,normally I50C cooler than the posterior pole, canbe produced experimentally with infrared radiation(Goldmann, 1932). However, the delayed-type ofmicrowave cataract usually is observed at theposterior surface of the lens and can be producedexperimentally more easily in albino than inpigmented rabbits (Daily and others, 1952). Here,

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FIG. 3 Anterior surface of lens, behind the iris (methylene blue, X 560). Note pigmented precipitates on lenscapsule and vacuolization of subcapsular epithelium

FIG. 4 Anterior surface of lens, near pupillary aperture (methylene blue, x 560). Note banded staining of thecapsule and vacuolization of subcapsular epithelium

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FIG. 5 Posterior surface of lens (methylene blue, x 560). Note irregular, outer capsule surface, and vacuolizationof subcapsular cortex

a direct heat effect from absorption by the pigmentof the iris seems unlikely.

There is a growing body of scientific data (Czerski,1974) demonstrating that long-term, chronic, orfrequently repeated exposure to low field intensitiesof non-ionizing radiation can produce non-thermaleffects on man. These are not associated withrecognizable signs or symptoms of whole or partialincreases in body temperature. In the lens, theclinical observation of a long latent period measuredin months or years between exposure and effectsuggests that these lesions are not produced directlyby a local increase in temperature during irradiationof the tissue. In addition, the adhesions betweeniris and lens capsule also develop later. Thesefindings suggest that perhaps the radiant energydamages the lens capsule directly (Zaret, 1972),altering its permeability or elasticity, therebydisrupting normal protein metabolism in the adjacentlens fibres. The injured capsule and subsequentpermeation of proteolytic products through it mayresult in a proteopexic adhesion to whateveradjacent tissues lie in contact with the lens. Sucha process could explain the clinical findings ofadhesions of the lens capsule not only to the irisbut also to the face of the vitreous and thus provide

a rationale for the delayed development of theseadhesions.

In Case 2, the maculopathy is indistinguishablefrom that seen in radiational chorioretinitis afterrepeated exposure to infrared radiation over anextended period of time. However, it is moreimportant to note that capsular opacification hasjust become evident in the left lens, indicating thatcataractogenesis is at a very early stage. Althoughone would anticipate a slow progression of theradiational injuries should the exposures continue,as a preventive measure the patient was advised todiscontinue unnecessary, further exposure to anyintense source of radiant energy, including theelectric oven and stove.

SummaryThe case histories of two individuals exposed tothermal radiation emitted from an electric ovenand range were presented. In one patient, earlierexposure to medical diathermy appears to haveinitiated delayed or late-appearing, capsular cata-racts. Instead of the anticipated slow progression,the cataractogenesis was accelerated followingrecent, repeated exposure to the intense, infrared

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FIG. 6 Posterior surface of lens (methylene blue, x 56o). Note banded staining of capsule and degenerated areasof subcapsular cortex

radiation. In the other patient, exposed solely toinfrared radiation, a chorioretinal lesion indistin-guishable from the type characteristically secondaryto repeated, thermal radiation was observed. Morerecently, the earliest sign of thermal radiationcataractogenesis, capsular opacification, has becomeevident.

The widespread availability of radiant energysources such as diathermy machines, microwaveovens, and electric ovens and ranges makes itimperative to examine carefully any possible hazardsthat may result from their use. With this in mind,radiant energy should be considered in thedifferential diagnosis of cataractogenesis.

ReferencesBOUCHAT, j., and MARSOL, C. (I967) Arch. Ophtal. (Paris), 27, 593CZERSKI, P., ed. (1974) 'Biological Effects and Health Hazards of Microwave Radiation, Proceedings of an

International Symposium'. Polish Medical Publishers, WarsawDAILY, L., WAKIM, K., HERRICK, J. F., PARKHILL, E. M., and BENEDICT, W. I. (1952) Amer. 7. Ophthal., 35, 1001

DUKE-ELDER, S. (I972a) 'System of Ophthalmology', vol. XIV, pp. 865-866. Mosby, St Louis(1972b) Ibid., pp. 888-894

GOLDMANN, H. (1932) Arch. Ophthal., 128, 648KURZ, G. H., and EINAUGLER, R. B. (I968) Amer. J7. Ophthal., 6, 866LANGLEY, R. K., MORTIMER, M. B., and MCCULLOCH, C. (I960) Arch. Ophthal., 63, 117RICHARDSON, A. W., LOMAX, D. H., NICHOLS, j., and GREEN, H. D. (1952) Amer. Jt. Ophthzzl., 35, 993SHIMKOVICH, I. S., and SHILYAEV, V. G. (1959) Vestn. Oftal., 72, 12VOGT, A. (1930) Klin. Mbl. Augenheilk., 85, 321WENZEL, M. DE (1786) Cited by S. Duke-Elder, in 'System of Ophthalmology', vol. XIV, p. 878. Mosby, St LouisZARET, M. M. (i964) Technical Documentary Report No. RADC-TDR-64-273, Cont. AF30 (602)-3087, p. 13.

Griffiss Air Force Base, Rome, New York(1972) IEEE Trans. biomed. Eng., BME-I9, 313(1974a) N.Y. St. . Med., 74, 2032(I974b) 'Biologic Effects and Health Hazards of Microwave Radiation, Proceedings of an International

Symposium', ed. P. Czerski. Polish Medical Publishers, Warsaw

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