Eyestrain (commonly called asthenopia) / by Ernest Clarke.

  • Ernest Clarke
Date:
1892
Catalogue details

Licence: Public Domain Mark

Credit: Eyestrain (commonly called asthenopia) / by Ernest Clarke. Source: Wellcome Collection.

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    causes great fatigue, vertigo, and sometimes vomiting. ^ And he says, vertigo appears to be the subjective correla- tion of want of co-ordination between the various muscular contractions necessary for adjusting the body to the different objects which surround it in space. . . . Vertigo is usually accompanied by motor phenomena in the region of distribution of the pneumogastric, such as feeble and irregular pulse, irregular respiration and vomiting. ^ The probability is that vertigo in all cases is a motor phenomenon^ and that although in many cases of ocular vertigo, the symptoms appear to be caused by retinal confusion, this very confusion causes a sense of instability. In diplopia the non-correspondence of the retinal images and the false projection, produce first a confusion, and this confusion produces a sense of want of equilibrium. Gowers says, There is an error in the unconscious in- ference of the relation of the body to seen objects, and this element in the impressions that influence the equilibria! centre is at variance with others, and either the discord or the disturbance of the centre is felt as giddiness. ^ The mechanism of vertigo is even more difficult to theorise upon, than headache. Physiologists agree that the cerebellum is the seat of equilibrium, and that organic or functional disturbance of this centre produces vertigo. By what path the contradictory sensory im- pressions find their way to the cerebellum is uncertain. The feeling of sickness, vomiting, dyspepsia and palpitation so often associated with vertigo are explained by the connection of the pneumogastric with the cerebellum. Gowers says, It is probable that the gastric fibres of the 1 Nervous System, 1883, vol. i., p. 436- 2 Ibid, vol. i., p. 92. Op. cit., vol. ii., p. 724.