The diaphragm test for binocular vision / by N. Bishop Harman.

  • Harman, Nathaniel Bishop, 1869-1945.
Date:
[1909]
Catalogue details

Licence: In copyright

Credit: The diaphragm test for binocular vision / by N. Bishop Harman. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    3. Exercises for squinters. Monocular alternate fixation, and binocular fusion can be practised through a series of graded tests, from coloured patches, pictures, and large letters to small print.* When one eye by reason of disuse has a lesser visual acuity than the other the superiority of the better eye can be reduced by paralysing the accommodation of that eye with atropine, by shading the half of the tests to be seen with that eye, or by placing such a glass before that eye as will reduce the vision to an equality with the weaker eye. 4. Detection of Malingerers. We cannot have too many tests'for the detection of feigned monocular blindness, but a good test must be Fig. 6. Fig. 7. Arrangement of test-card with The same test-card seen in coloured patches. the hole of the Diaphragm when the eyes are fixed on the pointer projecting into the upper part of the hole. simple. Here is one that is so simple that the surgeon cannot get tied up in using it, yet it is so subtle that an expert can be trapped. There are test cards with squares printed thereon, coloured, red and green, or black for use with the colour blind. The squares are printed right and left, any number may be used, but one each side is enough; and * A very cheap form of instrument with test cards is made for patients’ use.