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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    frequently associated with, and probably dependent on, inequality of the eyes, either in the way of astigmatism, myopia, or hypermetropia.^ Liveing says that the nerve storms in megrim have their point of departure or principal focus in the optic thalami, and that the normal course is from above down- wards (to the nuclei of the vagus), and from before back- wards in the sensory tract.^ This explains the peculiar visual phenomena such as teichopsia, &c., and other symptoms of ophthalmic megrim when the ocular trouble is the effect; but when it is the cause the point of departure must be in the eyes themselves or their con- nections, and the headaches must be brought about some- what as follows. The ciliary muscle, or the external muscles of the eye, or both, are being overtaxed, hence an excessive supply of blood is passing to them leading to active, and, if kept up, to passive, congestion. This con- gestion will not be limited to the muscles in question, but in time will pass to other parts of the eye, leading to watery red eyes, or in other words, to chronic conjunc- tivitis. This congestion will either cause, or make the muscles prone to, pain, and added to the pain of fatigue, will account for the feeling of tension or pain in the eyes themselves ; and the intimate connection of the nerves sup- plying these muscles with the fifth pair will cause the morbid action to spread to these latter nerves, and explain the frontal headache. Through the connection of the fifth nerve with the sympathetic, we can understand how this morbid action can travel to the dura mater, pia mater and sensory layer of the cortex of the brain ; and this action ' On the Pathology and Treatment of some Forms of Headache, St. Bartholomew's Hospital Reports^ vol. xix., p. 336. Op. ci/.., p. 306.
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