Miners' Diseases - 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

(a)	deficient illumination,
(b)	the assumed position of the miner at work,
(c)	noxious gases,
(d)	neurosis,
(e)	alteration of light intensity.

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),
(f)	shadows cast by the lamp limiting the area illuminated,
(g)	the direct glare of the lamp in the eyes of the workman,
	(i)	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.

The conclusion of the Nystagmus Committee is that the cause of the disease is defective illumination.

Preventive Measures may be summarised as follows:

(a)

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.

(b)

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.

(c)

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.