|Year : 1968 | Volume
| Issue : 4 | Page : 202-206
Radiation hazards to eyes in industry
|Date of Web Publication||24-Dec-2007|
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Pandit Y. Radiation hazards to eyes in industry. Indian J Ophthalmol 1968;16:202-6
The post World War II era has made the public conscious about radiation hazards. The atomic bombed areas of Hiroshima and Nagasaki have given material for thought, and the scientist today is trying to peep into the mysteries of radiation from different angles. Heister, 1739, was first to observe the effects of infrared radiation in glass blowers, whilst the radiation effect with X-Rays and Gamma rays upon the eyes was observed in the early roentgen era by Birch Hirschfeld in 1904. He also mentions the radiosensitivity of the eye of the fetus and the new born animals. Prior to this in 1897 Chalupechi first described the effect of irradiation on the eyes of rabbits. In 1907 Tribondean and Lafrague produced irradiation cataracts. "Ionizing radiation, tell nobody of their presence" says Professor Mayneord "and that rise of great industries dependent on the production of radioactive materials as their basic process necessarily introduces new hazards on a large scale, both to the individual worker and the general population." For the past two decades reports are published from all countries on the subject of radiation injuries. The study has been carried out from different angles like clinical study, histology and histobiology, mechanical changes, E.R.G., biochemical changes, study of the distance from the centre of radiation, animal experimentation etc. In these particular studies the eye has an important bearing in as much as (i) studies can be carried out on an isolated retina and (ii) the lens is an avascular capsulated stricture where repair to damage is hardly possible, and no outside agency can take away the damaged tissue; (iii) it is more easily accessible to study in more ways than one.
Our own clinical study has been carried out on glass blowers but for the rest of the material in absence of any specific studies in this direction it is purely 'Library research'. Before we give the details of some observations in experimental work we should like to place before you some clinical facts about the atomic radiation cataract.
Work, by Dodo suggests that incidence to cataract diminished sharply in radiations beyond 1600 metres from the hypocentre. He classifies these cataracts in four grades.
Cataract cases from irradiation seen at a radiation distance 900 metres from the hypocentre in 1957 and 1966 show no appreciable change, Masuda, 1966, has given some detailed records of his findings in 1101 sufferers. He feels that 96 or 8.7% have atomic cataract; 121 or 11% have suspicious atomic cataracts. According to age the percentage is greater n people under 25 years 10.2% than over 26 yrs. 8.8%.
He gives the exposure distance as follows: with percentage;
Within 2 Km 79 cases (10.9%)
Within 2-3 Km 11 cases (4%)
Within 3-4 Km 3 cases (5%)
Within 4-5 Km 3 cases (7.5%)
Cataracts with signs and symptoms were seen in 68 cases or 11.3% and cataract without signs and symptoms was seen in 28 or 5.6%
He described the changes as follows:
Granular atypical opacities 54%;
Disciform changes 27%;
vacuoles; plate like opacities, star figure opacities, in the rest.
Dosage of Radiation: There is some difference of opinion. Cogan for a distance of 1.97 Km places r-ray from atom bomb as 600r and neutron 3-15rep. Shone gives the neutron value as 280rep. This is the momentary dosage. A residual dose also occurs 100r during 100 hours. Hirose, gives the relation between incidence of the atom bomb cataract and doses of r-ray and neutrons. Between 0-49 radius 11.9% increases between 200 to 499 rad 55.3% and over 500 rad to 90%.
Tokunaga is of the opinion that the severity of the cataract is dependent on the dosage of the radiation. He and Hirose place visual disturbances in 5% of the cases.
Hirose, Tokunaga, and Inoda et al undertook slit lamp studies and described the following four groups:
(i) limit opacities;
(ii) Polychromatic posterior plaque opacities;
(iii) Roughness of posterior plaque opacities
(iv) thick opacities.
Histologically Dodo feels that the nests of granular fragments or broken down lens fibres are seen in the subcapsular region. Tokunaga mentions the fibril dilatation of the posterior lens, ectopic cells in the posterior capsule and abnormal swelling of fibres. On electron microscopy he finds a dissociation parallel to lens fragments and an ectropion of the lens epitheioid cells leading to fibroblast cells and degeneration.
Having placed before you this brief clinical and histological outline, let us see what further interpretation and knowledge we can gain by experiment and research at the present day.
Most of the studies are with ionizing radiation on animals, mammals, nocturnal moths, hen, frog, rabbit, brown moths etc. It comprises of a detailed study of the radiation strength, and the morphological, histological, chemical, biochemical, histobiological and ERG changes produced by it. The modes of radiation employed are the X-Rays, beta Rays, and Neutrons.
Let us first consider the changes produced by irradiation on the lens. It is now common knowledge that microwaves, heat waves, ultraviolet light, and ionising irradiation can all produce cataracts. The radiogenic cataracts are symmetrical with a situation at the posterior pole and appear as small radial opacities. The animals used for experiments are mostly rabbits and rats. Von Sallmann et al 1955, Cogan et al 1953 Kandori 1956, Krause and Bond 1951 opine that there is no difference between the different types of ionising radiations used or the response to them in different species of animals. Clinically the lens changes appear after a long latent period depending on the magnitude of the dose, distance from the hypocentre, age of the animal and several other factors. It also makes a difference if the whole or part of lens is irradiated. The younger the animal the shorter is the period during which a change occurs and the changes are most extensive. Histologically the lens epithelium shows changes in hours, days, months following radiation. Poppe 1942, Cogan and Donaldson 1951; Von Sallmann 1955 found (i) a fall in the rate of mitosis in half an hour followed by cessation of mitosis for 2-6 hours; followed by excess of mitosis, fragmentation and later breakdown of the epithelium. If the lens is shielded in part and irradiated, results show that axial irradiation does not lead to opacity; irradiation of the whole lens leads to cataract; while irradiation of half of the lens gives rise to vacuole formation in the area irradiated. A fairly common view exists that the cataract is the product, an indirect one, from the radiation effects of the ciliary body. Devik 1957, Pirie and Drance 1959 have shown that irradiation of the ciliary body leads to cataract formation. Kandori 1956, Pirie 1959 were unable to produce cataracts in pigeons and chickens.
Dosage: Experimental work by Rados; Schiz and Roberschneider suggests that the lens is the most radiosensitive tissue. A single dose of 500 to 800 r. can cause cataract in man. X-Rays up to 100 to 1200 Kv are less penetrating and affect mostly the anterior segment. More penetrating radiations affect the lens. Fractionation of X-Ray doses does show a cumulative effect. Beta radiation can produce cataract but a dose ten times as much is required through the centre of the cornea. Neutron radiations as shown in mice, rabbits and dogs are more effective than X-Rays, in producing cataracts. The threshold dose according to Upton et al is 150 rep for neutrons. Ham 1953 gives it as 45 rep for man. It varies with the animal. Shiglo and Masuda 1955 have shown that in atomic radiations, in high dose exposures the cataract may appear several years after irradiation. Cyclotrons emit radiations of neutrons and r-rays. All cataracts in industrial workers are amongst the cyclotron operators. Hans-1953 gave a figure of 21. It should be remembered that fast neutrons from cyclotrons or from Po-B and thermal neutrons are 2-4 times as effective as 250KV X-Ray or 3-4 times as effective as 1-2 MeV r-rays.
| Biochemical changes|| |
Histological: damage to nuclei occurs within half an hour of irradiation and staining is possible with desoxyribonucleic acid after a period of two weeks. Chemically there is decrease in the glutathione and this glutathione decrease continues as the lens becomes opaque and then it is completely destroyed.
Administration of cysteine, thiourea, glutathione, cystamine, before irradiation reduces the harmful effects of radiation. Cysteine is very effective in this condition and may act in one of the two possible ways. (a) by itself accepting the radiation thus reducing the amount of radiation to the lens and (b) it ability to prevent mitosis. (Sallmann, Swanson, Francois). The chemical changes observed are the reduction in glutathione of the lens; a fall in the ascorbic acid in the aqueous; fall in enzyme glycoxalate, and acetaldehyde oxidase and reduction of desoxynucleic acid in the lens epithelium.
Cataract in the nuclear physicists: Abelson and Kougar (1949) reported cataracts in nuclear physicists. Ham in 1953 recorded 2 cases from those injured in nuclear explosions. This was caused by fast neutron and hard r-rays.
| Radiation effect on other tissues of the eye|| |
a. Retina: Studies have been carried out on isolated retina and intact retina. It is observed that an isolated retina is injured more than intact retina by radiation.
Demirchoglyan et al 1965 studied the action of ionising radiation on the retina adopting the following, methods: i) use of contact lens and prolonged flashes; ii) determination of ERG adaptation; iii) measurement of intraocular pressure; iv) determination of blood components and v) the weight of the animals. They found in the early stages a radiation sickness, with increased fluctuation in the ERG; a tendency to leukopaenia, disturbances of higher nerve reflex activity, and later cataract. Increase in radiation causes minor changes in photo-receptors but the nerve fibres of the ganglion cells are least affected. It is apparent that a phenomenon of radio-phospherence occurs in the retina and the scotopic areas are much more affected, the rods are generally affected. Marmur and Manturo 1966 state that the vulnerability of the retina to radiation is disputed in view of two reasons (i) retinal membrane is considerably radio resistant, (ii) retinal membrane has high sensitivity. Using six months old chinchilla rabbits weighing 1500 to 1700 kg they gave single X-radiation of 1 KR; 5 KR; 10 KR to different batches and studied the histopathology at different intervals after irradiation. In the first case of 1 KR they obtained focal damage in the nuclear layer with a partial penetration of the rod layer, a decreased staining of cells and hyperchromatolysis of the ganglion layer. The whole thing suggested a mosaic pattern. There appeared some signs of reversibility. With 5 KR within 1 to 3 hours there was focal damage in the outer molecular layer, reduced staining of the ganglion cells, and hyperchromatosis of the inner nuclear layer. These changes were more substantial on the 5th day, with fine granular breakdown of the rod and cone laver. With 10 KR, substantial pathological changes are seen on the tenth day. These are a breakdown of the rod and cone layer, death of inner and outer molecular layer, loss of histological structure of large ganglion cells and exfoliation of the retinal membrane. Peps has shown that rhodopsin is decolorised by heavy doses of roentgen.
The Choroid: M. Perreres; Taylor; D. Brinkley, Tegwedd Reynolds; (1965) discuss choroidoretinal changes as complications of radiotherapy. They have recorded their minute observations on patients undergoing radiation treatment near the eye for a period of 14 years. The changes found in 24 persons out of 119 are punctate keratitis, atrophy of the iris, glaucoma, cataract; The changes observed in the posterior segment are i. temporary choroidal pallor, with constriction of the retinal vessels, ii. atrophy of the choroid and retina with pigment at the edge, iii. acute choroiditis with fluffy edge iv. retinal changes simulating hypertension retinopathy.
ERG studies have been carried out on the irradiated retina and show a -ve a wave; a positive b wave; a continuous positive c wave; and when stimulus ceases a d wave.
ERG shows an effect on the functioning of the eye in low dosage. ERG is suppressed with 3000r.
In mallow moth the ERG may show a weak recording or may be absent. Other effects: Roentgen and gamma radiation affect all parts of the eyes. It leads to necrosis of the lid cartilage, suppression of lacrymal secretion; telengiectasis of the conjunctiva; lack of lustre of the cornea and growth of vessels and ulceration.
The Visual pathway: We have covered the receptors, we must now consider the conducting paths. Experimentally it is found that receptor output to C.N.S. can be altered by irradiation. If a-particles are placed on the cats tract, first there is enhancement and later loss of conduction. 400 to 1200 r radiations to rabbits' head lead to alterations of ERG records from the lateral geniculate body and the visual cortex in response to flashes of light. In hens, radiation of the head leads to "Opticogenic catalapsy".
There is loss of visual sensibility as a descrimination in visual behaviour. This is more of the scotopic type.
In conclusion I may say that the work on irradiation has something interesting and as industrial growth is one of the main aims in the country today, some of the younger generation should take interest in it and the Council for prevention of blindness should make necessary facilities available for this important research.
I wish to convey my sincere Thanks to Atomic Energy Establishment, Trombay, for their kindness in providing and allowing me the use of the literature.
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