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

  • Edward Jackson
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)

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    CHAPTER I. HISTORY, NAME, DIFFICULTIES, AND METHOD OF STUDY- ING THE TEST. History.—From the earliest use of the ophthalmoscope it has been recognized that, by the direct method, the see- ing of an erect image of the fundus at some little distance from the eye indicated hyperopia, and the seeing of an in- verted image indicated myopia; and that the distance of the inverted image from the eye indicated the degree of myopia. So long ago as ^862, Bowman (27ie Royal London Ophthalmic Hospital Reports, Vol. II, p. 157), called atten- tion to the rotation of the mirror as a' means of bringing out appearances characteristic of irregular astigmatism and conical cornea, and Bonders, in his work on Accommodation and Refraction of the Eye, published in 1864, includes (p. 490) the following note : My friend Bowman recently informs me that 'he has been sometimes led to the discovery of regular astig- matism of the cornea, and the direction of the chief meridi- ans, by using the mirror of the ophthalmoscope much in the same way as for slight degrees of conical cornea. The observation is more easy if the optic disc is in the line of sight and the pupil large. The mirror is to be held at two feet distance, and its inclination rapidly varied, so as to throw the light on the eye at small angles to the perpendi- cular, and from opposite sides in succession, in successive meridians. The area of the pupil then exhibits a some- what linear shadow in some meridians rather than in others.'
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