Colour-blindness and other defects of sight in some of their medico-legal aspects / by James T. Tudall.

  • Rudall, James T.
Date:
1887
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Licence: Public Domain Mark

Credit: Colour-blindness and other defects of sight in some of their medico-legal aspects / by James T. Tudall. Source: Wellcome Collection.

Provider: This material has been provided by UCL Library Services. The original may be consulted at UCL (University College London)

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    of persons with refraction errors ? Have they been detected by the examiners, and prevented from entering the railway service? If so, nothing of the kind has been stated. If they have not been detected we must suppose that there is now employed on the Victorian railways a very large number of persons with defective sight, and therefore, in the very words of the railway Medical Inspector, liable to occasion the most fearful calamities. Why should it have been concluded that because a person can match coloured wools, which he may hold six or twelve inches from his eyes, he can also of necessity distinguish coloured railway signals at eight hundred yards, and ships' lights at two miles distance ? It does not seem probable, and, moreover, it is not the case. Dr. Brailey has shown that an error of refraction of only one dioptre may • diminish the distance at which coloured lights can be dis- tinguished, by one-half, and I have repeatedly made similar observations myself Within a few days, I have seen a person (A), the subject of slight hyperopic astigmatism, who read nearly ^i. Donders's spots were only distinguished at five feet, and a 2}4 mm. diameter green disc by transmitted light was scarcely made out at ten feet. With a correcting convex cylinder (-f- ry. iD), the spots were made out well at ten feet, and the green light at fifteen feet. Another case (B) was the subject of a myopia of ten dioptres. The spots were made out at eighteen inches, and the green light at three feet. Nearly corrected with a concave len.s, the spots were seen at three feet, and the green light was well perceived at twelve feet. So important, then, is the refraction as concerns the colour perception at a distance. Again, it would appear that the railway Medical Inspector leaves quite out of account all cases of acquired colour defect. What says Dr. Brailey ?— The various conditions requiring spectacles, defects of form and colour arising from the use of tobacco and, perhaps, of alcohol—those due to nervous diseases, too many of them of syphilitic origin, arc at least as common among sailors as among landsmen. When we add to these, congenital defects of colour, and also such conditions as glaucoma and cataract, we become impressed with the gravity of the subject. How common are these defects we shall never know exactly till the authorities wake up from their present apathy, and step in with some legislation. These remarks and quotations will fail of their purpose if they do not lead some persons, at least, to perceive that the practical testing of sight does not