Skiascopy and its practical application to the study of refraction / by Edward Jackson.

  • Jackson, Edward, 1856-1942.
Date:
1898
Catalogue details

Licence: Public Domain Mark

Credit: Skiascopy and its practical application to the study of refraction / by Edward Jackson. Source: Wellcome Collection.

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

    12/122 (page 8)
    The use of the ophthahuoscope above referred to, for the detection of irregular astigmatism, became widely pop- ular. It was generally adopted as the most satisfactory test for this kind of defect. But the observation that the same method was capable of revealing regular astigmatism and the direction of its principal meridians, does not seem to have attracted general attention. In 1872, Couper, in his paper before the Fourth Inter- national Ophthalmological Congress (see Trans, page 109), alluded to Bowman's observations, and said : The greater dispersion in one meridian than in the opposite, gives rise to the linear shadows. Only the fact of astigmatism is thus established. He then went on to describe a method of using the ophthalmoscope as an optometer in astigma- tism, which is rather a modification of the ordinary use of the ophthalmoscope than a variety of skiascopy, since it depends on the recognition or non-recognition of the retinal vessels in different meridians, when the ophthalmoscope mirror is held at a considerable distance from the eye, and takes no account of the movement of a light area on the retina. In 1873, Cuignet, of Lille, published (Rec. d'Ophtal- mol, 1873, pp. 14 and 316) an account of the test, as he had used it, as one capable of revealing not only the pres- ence of hyperopia or myopia as well as astigmatism, but also as giving a practical method of measuring the amount of these errors of refraction. He seems not to have appre- ciated fully the optical principles involved in the test, and his account of it attracted no attention. However, in 1878, his pupil, Mengin, introduced the practice of the method at Galezowski's clinic in Paris. There it was taken up, and Parent demonstrated its true optical basis and urged its advantages in a series of articles published in the Remeil d' Ophtalmologie in 1880-81, pp. 65 and 229. Lytton Forbes, in the Royal London Ophthalmic Hos-