The detection of colour-blindness and imperfect eyesight : with a table of coloured Berlin wools and sheet of test-types / by Charles Roberts.

  • Roberts, Charles, 1836-1901.
Date:
1884
Catalogue details

Licence: Public Domain Mark

Credit: The detection of colour-blindness and imperfect eyesight : with a table of coloured Berlin wools and sheet of test-types / by Charles Roberts. 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.

    18/26 page 14
    THE DETECTION OF COLOUR-BLINDNESS BY THE TABLE OF COLOURED WOOLS. (See the table of Wools on the cover.) An explanation of the table of coloured luools is given on the page facing the table at the end of the book. No decisive results can be obtained as to the efiBicacy of a person's colour-sense by asking him the names of colours. One person's per- ception of colours may be good, yet his power of expression may be defective; whereas another may be colour-blind, but practice may have taught him the names of colours. The table of coloured wools has been marked with numbers, so as to avoid the necessity both for the examiner and the candidate to designate the colours by their names, and it is only required that the person under examination should reply in the affirm- ative or in the negative to the examiner's questions. The wool patterns are already sorted, as they would be by colom'-blind persons tested by Holmgren's method. The table contains ten horizontal lines, one of which contains samples of different colours (No. 1), and two are filled with one colom- in various shades according to the degree of hght (No. 2, red; and No. 8, green). Test I.—The table should be placed in good daylight, and the candidate should be told that some of the horizontal lines contain colours of one description in different shades, and others different colours; after which, the first line should be pointed out, and the candidate questioned whether all the colours therein are of the same description, which question should be repeated with each consecutive line. Diagnosis 1.—If the candidate designates the two uni- coloured lines (i. e. No. 2 and No. correctly, and dismisses ^ all the rest as mixed, his colour-sense may be considered good. 2, —But if he does not designate them correctly, nor any of the others, his colour-sense is undecided. 3. —If he designates one of the lines with various, colours ' as being all of the same colour, he is .^lmir:blind, and he will have great difficulty in distinguishing between green and red. 13 k ri^lti (0
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