Subjective symptoms in eye diseases : being chapters on the disorders of vision symptomatic of diseases in the eye and central nervous system / by George A. Berry.

  • Berry, George A. (George Andreas), 1853-
Date:
1886
Catalogue details

Licence: Public Domain Mark

Credit: Subjective symptoms in eye diseases : being chapters on the disorders of vision symptomatic of diseases in the eye and central nervous system / by George A. Berry. 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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    direction unless no increased measurement resulted from testing with a lower point of fixation. The determination of the limits of the field for different colours is a matter of much greater difficulty and uncertainty, as the results are influenced by the hue and shade of the colour used, by the size of the coloured objects, and by the quality and intensity of the light under which the examination is conducted. Practically, in examining any case, I find it useful to determine the extent of my own visual field in one or two directions under the same conditions, and then allow something for individual peculiarity besides. Another precaution that will be found useful in practice is to have the test object (which it is well to make 20 mm. square) differently coloured on either side. In this way we are provided with a check on the accuracy of the patient's statements. The most convenient colour to use is some hue of red, as it is for the reds and greens that pathological defects in the colour sense first manifest themselves. If the test colour chosen be examined carefully at the inner side of the field of vision, it will generally be found to change colour. Before becoming ab- solutely colourless, it will become yellowish, brownish, or bluish, according to the hue and shade selected, and it is this tint which may with advantage be selected for colouring the opposite side of the test object. When the red-green perception is entirely abolished, the limits may be taken for blue or yellow, the vision for which is longer in disappearing, but the only necessity for this is to exclude the possibility of the more usual form of congenital colour-blindness, which we should have reason to suspect if the peripheral boundaries for yellow and blue were not restricted. But the determination of the limits of the field for quantitative and qualitative stimuli does not exhaust the examination of in- direct vision: it is important to ascertain whether or not there is any break in the continuity of the field. Such interruptions, or scotomata, are usually divided into -positive and negative, according as they give rise or not to a consciousness of the interruption. In the one case there is more or less perception of darkness, in the other an entire absence of any visual impression. The scotoma