Nystagmus
This is an occupational disease affecting
the nerves of the eyes, causing a spasmodic movement
of the eyeball, either rotary or from side to side.
According to Home Office statistics, nystagmus is the
most widely prevalent of all industrial diseases, and
is found only among miners.
The causes of nystagmus have been given by experts as
arising from
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(a)
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deficient
illumination,
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(b)
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the
assumed position of the miner at work,
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(c)
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noxious
gases,
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(d)
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neurosis,
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(e)
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alteration
of light intensity.
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Symptoms
The first symptom is failure of sight.
Later the sufferer complains of lights and other objects
dancing before his eyes. He then complains of giddiness
and headache, particularly across the temples and at
the back of the head, inability to see at night, and
dread of light. These symptoms are most marked after
exertion or stooping.
The physical signs of the disease are the characteristic
involuntary and irregular rotary movement of the eyeball,
and twitching of the eyelids and eyebrows when the man
is exposed to any light.
One of the most characteristic signs of the disease
is the failure of what is known as the dark adaptation
sense. This is inability to adapt oneself to darkness
on first leaving the light.
The types of cases may be divided into two: first, the
"Latent," in which oscillation is slight and
there is no disability; and second, the "Active,"
in which there is either partial or total incapacity.
The mental condition of the miner consequent on his
anxiety and lack of confidence cannot be overlooked.
The erroneous belief that the disease causes loss of
sight has often caused unnecessary suffering and the
development of psycho-neurotic symptoms.
Some men having latent nystagmus may be able to work
for years with very little discomfort, whilst those
who have the disease in its active form have to do work
on the pit bank, or leave the pit for a time.
Causes of Nystagmus
Although all classes of underground
workers are affected, at least 8o per cent. of cases
are coal-face workers, where the illumination is bad.
In the naked-light districts of Scotland and the Forest
of Dean, it is not so common as in the safety-lamp districts
in the North Midlands. This suggests that the relatively
poor illumination of the safety lamp is more detrimental
to the eyes than the illumination of the candle. Illumination
at the coal face is dependent on several factors, i.e.
| [a] |
the candle power of the source of illumination, |
| [b] |
the
distance from the face at which the lamp
must be placed, |
| [c] |
the
surface brightness of the surrounding
objects, which is small, |
| [d] |
the
absorption by blackened surfaces of most
of the incident light, |
| [e] |
the
effect of ventilation (the lower the oxygen
percentage in the air the poorer the light),
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| [f] |
shadows
cast by the lamp limiting the area illuminated, |
| [g] |
the
direct glare of the lamp in the eyes of
the workman,
a dust-laden atmosphere absorbs more light
than a clear one and the dust fouls the
lamp glass, |
| [h] |
the
alternation of light intensity where men
travel in groups over long distances,
carrying unshaded lights. |
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The conclusion of the Nystagmus
Committee is that the cause of the disease is defective
illumination.
Preventive Measures may be summarised as follows:
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(a)
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Increase
the illumination of the pit bottom and
roadways, as far inbye as possible, by
the use of whitewash or light-coloured
stone dust. This will enable the dark
adaptation process to be can-led out as
quickly and comfortably as possible, and
the man will get his "pit eyes"
the more easily.
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(b)
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Every
workman should carry a piece of tin to
shade his lamp, or one half the surface
of the lamp glass should be frosted, to
prevent inconvenience to those following.
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(c)
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Glare
should be avoided by the use of a shade
or tinted glass. It must be borne in mind,
however, that frosted, tinted, diopteric
glasses, and the like, seriously affect
the illumination.
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