Influences of school life on eyesight : being the substance of a lecture delivered before the Sheffield and District Certificated Teachers' Association, on January 12th, 1884, and published at the request of the Committee / by Simeon Snell.

  • Snell, Simeon, 1851-1909.
Date:
1884
Catalogue details

Licence: Public Domain Mark

Credit: Influences of school life on eyesight : being the substance of a lecture delivered before the Sheffield and District Certificated Teachers' Association, on January 12th, 1884, and published at the request of the Committee / by Simeon Snell. Source: Wellcome Collection.

Provider: This material has been provided by The University of Leeds Library. The original may be consulted at The University of Leeds Library.

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    In the normal eye, distant rays of light are brought to a focus on the retina, and for near objects, with the aid of what is called accommodation, by increasing the convexity of the lens, this is still the case. In the myopic or short- sighted eye, the pencil of light meets, however, in front of the retina, whilst in the hypermetropic, or long-sighted, the point of union is behind the retina. Besides these, there is a third deviation, called astigmatism, in which the curvature of one meridian is different from that in the other. The effects resulting from this last-named condition are relieved by the employment of the appropriate spectacles ^cylindrical), and we shall not have occasion to particularly refer to it, separately from the other “ errors of refraction ” I have mentioned. The eye naturally seeks after a clear image, and it will be at once evident, that with the long-sighted—if we consider this condition first—under ordinary circumstances this cannot be obtained. For the hypermetropic child is only able to bring the rays of light to a focus on the retina by an extra use (strain) of the focussing muscle ; this it is enabled to accomplish for a time, but after a longer or shorter period, according to the degree of the defect, with comfort it is no longer possible. Then, after reading, the print in the book or, in working, the stitches in the garment run all together, become indistinct, the eyes tire, and the child seeks relief by closing the eyes ; again, however, on resuming its task the symptoms recur. This constant strain is without doubt, causing as it does congestion of the globe, of detriment to the eyeball, and the nervous irritation becoming reflected is a frequent source of the headache so common among school-children. The symptoms mentioned are relieved by properly-correcting convex spectacles. And then there is no reason why the long-sighted child should not become a good scholar. In such a case as has been portrayed, some- times, instead of the little muscle performing the focussing of the eye becoming relaxed, when the eye is no longer intent on near work, it remains constantly on the strain, a condition of “ spasm ” being produced, and causing a ficti- tious short-sightedness. If a qualified surgeon has not seen