Refraction of the eye : its diagnosis and the correction of its errors with a chapter on keratoscopy / by A. Stanford Morton.

  • Morton, A. Stanford.
Date:
1882
Catalogue details

Licence: Public Domain Mark

Credit: Refraction of the eye : its diagnosis and the correction of its errors with a chapter on keratoscopy / by A. Stanford Morton. Source: Wellcome Collection.

    17/76 (page 5)
    CHAPTER II. Definitions. Def. I. The refracting-surfaces of the eye are, according- to Bonders—a, the anterior surface of the cornea ; b, the anterior surface of the lens; c, the anterior surface of the vitreous. The transparent media together form the Diop- tric system of the eye, which has an action similar to that of a biconvex lens. Def. 2. Refraction 0/the eye means the effect which, by reason of its form and structure, this organ exerts upon rays of light entering it when completely at rest. Fig. 3. Def. 3. In Emmetropia (Fig. 3) parallel rays, k.a, come to a focus upon the retina, F, when the eye is at rest. Conversely, rays from the retina emerge parallel from the eye. Def. 4. An Ametropic eye is one in which, when at rest,. parallel rays do not come to a focus upon the retina. As will be seen from the four following definitions, it may be either Myopic, Hypermetropic or Astigmatic. Def. 5. A Myopic eye (Fig. 4) is that in which, when at