Eye Injuries Due to Radiation
By Edouard Bastarache
1-Injuries Due to Ionizing Radiation :
X-rays, beta rays, and other radiation sources in adequate doses can cause
ocular injury.
A) Lids:
The eyelid is particularly vulnerable to x-ray damage because of the thinness
of its skin. Loss of lashes and scarring can lead to inversion or eversion (entropion or
ectropion) of the lid margins and prevent adequate closure.
B)Conjonctiva :
Scarring of the conjonctiva can impair the production of mucus and the
function of the lacrymal gland ducts, thereby causing dryness of the eyes.
C)Lens:
X-ray radiation in a dose of 500-800 R. directed toward the lens surface can
cause cataract, sometimes with a delay of several months to a year before the
opacities appear
2-Injuries Due to Ultraviolet Radiation :
A) Cornea:
Ultraviolet radiation of wave lengths shorter than 300 nm. (actinic rays) can
damage the corneal epithelium. This is most commonly the result of exposure to the sun at high
altitude and in areas where shorter wave lengths are readily reflected from bright surfaces such as
snow, water, and sand.
Exposure to radiation generated by a welding arc can cause welding flash burn
, a form of keratitis.
B) Lens:
Wavelenghts of 300-400 nm. are transmitted through the cornea, and 80% are
absorbed by the lens, where they can cause cataractous changes.
Epidemiologic studies suggest that exposure to solar radiation in these wave
lengths near the equator is correlated with a higher incidence of
cataracts.
They also indicate that workers exposed to bright sunlight in occupations
such as farming, truck driving and construction work appear to have a higher incidence of
cataract than those who work primarily indoors.
Experimental studies have shown that these wave lengths cause changes in the
lens protein, which lead to cataract formation in animals.
3-Injuries Due to Visible Radiation (Light):
Visible light has a spectrum of 400-750 nm. If the wavelengths of this
spectrum penetrate fully to the retina, they can cause thermal, mechanical, or
photic injuries.
A) Thermal injuries:
They are produced by light intense enough to increase the temperature in the
retina by 10-20C.
Lasers used in therapy can cause this type of injury. The light is absorbed
by the retinal pigment epithelium, where its energy is converted to heat, and the heat causes
photocoagulation of retinal tissue.
B)Mechanical injuries:
They can be produced by exposure to laser energy from a Q-switched or
mode-locked laser, which produces sonic shock waves that disrupt retinal tissue.
C)Photic injuries:
They are caused by prolonged exposure to intense light , which produces
varying degrees of cellular damage in the retinal macula without a significant
increase in the temperature of the tissue.
Sun gazing is the most common cause of this type of injury, but prolonged
unprotected exposure to a welding arc can also damage the the retinal macula.
There may be permanent decrease in visual acuity.
The intensity of light, lenght of exposure, and age are all important
factors. The older ones are more sensitive, also those who have had cataract
surgery because filtration of light by the lens is impaired.
4-Injuries Due to Infrared Radiation:
Potters may be exposed to this type of radiation.
Wavelenghts greater than 750 nm. in the infrared spectrum can produce lens
changes.
La "cataracte des verriers"( glassblower's cataract ) is an example
of a heat injury that damages the anterior lens capsule among unprotected
artists. Denser cataractous changes can occur in unprotected
workers who observe glowing masses of glass or iron for many hours a
day.
Another important factor is the distance between the
worker and the source of radiation. In the case of arc welding, infrared
radiation decreases rapidly as a function of distance, so that farther than 3
feet away from where welding takes place, it does not pose an ocular hazard
anymore but, ultraviolet radiation still does. That is why welders wear tinted
glasses and surrounding workers only have to wear clear ones.
Conclusion:
When we speak of type of exposure, potters look at their
cone packs for very short periods of time in a repeated way, more often nearing
the end of firing; and also according to the use of other methods for measuring
temperature, like the concomitant use of a thermocouple and a reading device.
So, these " short-term " exposures are spaced by quite
longer " exposure-free " periods and the sum of the former
does not correlate with the concept of "many hours a
day".
We have searched the literature pertaining to Occupational Health and Safety
and have not found a single case of presumed " ceramicist's or
potter's cataract ", even if the trade of potter is quite older than
the one of glassblower.
Therefore, I do not think that any of the above types of radiation present a
threat to potters.
It is a good thing, mainly at high temperature, to wear lightly tinted
industrial grade safety glasses to better visualize cones(ocular ergonomics) and
also to reassure those who are more worried.
These glasses also offer a better protection than typical sun-glasses in case
of projection of hot dust particles from a gas kiln when looking through the
peephole in a soft brick door.
By the way with ageing, most if not all of us, will suffer from cataracts of
the "senile" type.
The progress or change and the related reduction in vision is usually quite
slow.
Nuclear sclerosis-an increasing density in the central mass of protein-causes
a myopic change than can be corrected by changing glasses for some years-in many
instances restoring vision to near normal.
References :
1-Occupational & Environmental Medicine, Joseph Ladoue & al, last
edition.
2-Occupational Medicine, Zenz C., last edition.
3-Precis de Medecine du Travail, Desoille H., Scherrer J., Truhaut R., last
edition.
4-Oshline & Nioshtic database.
Edouard Bastarache M.D.
Occupational & Environmental Medicine
Author of "Substitutions for Raw Ceramic Materials"
Tracy, Québec, CANADA
edouardb@sorel-tracy.qc.ca
http://www.sorel-tracy.qc.ca/~edouardb/
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