Refraction of the eye : its diagnosis and the correction of its errors / by A. Stanford Morton.

  • Morton, Andrew Stanford, 1848-1927.
Date:
1897
Catalogue details

Licence: Public Domain Mark

Credit: Refraction of the eye : its diagnosis and the correction of its errors / by A. Stanford Morton. 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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    the retina. Such an eye may be either myopic, hyperme- tropic, or astigmatic. Dkf. 5.—a myopic eye (Fig. 4) is that in which, when there is no accommodation, parallel rays come to a focus in front of the retina, as at F. Conversely, rays issuing from the retina R, which is behind the principal focus of the Fig. 4. dioptric system, emerge as convergent rays (Chap. I., c) which meet at a point M in front of the eye. Rays pro- ceeding from this point (called the far point) would therefore be focussed on the retina. Fig. 5. Def. 6.—A hypermetropic eye (Fig. 5) is that in which, when there is no accommodation, parallel rays (Aa, B5) are so changed in direction that they tend to come to a focus at F, behind the retina. Conversely, rays proceeding as if from F would emerge from the eye parallel to one another. Rays, therefore, from R, which is situated ivithin the focus of the dioptric system {vide Def. i), emerge from the eye diverging (Chap. \., d) as if they were proceeding from a point G. The distance of this point behind the front part (nodal
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