The refraction of the eye : a manual for students / by Gustavus Hartridge.

  • Gustavus Hartridge
Date:
1886
Catalogue details

Licence: Public Domain Mark

Credit: The refraction of the eye : a manual for students / by Gustavus Hartridge. Source: Wellcome Collection.

    137/272 (page 117)
    APHAKIA ]17 it is possible to see tlie details of tlie fundus clearly, is tlie measure of the total hypermetropia, Fig. 43. Asthenopia and convergent strabismus, two of the most frequent results of hypermetropia, will be treated of in Chapters IX and X. See Cases 1 and 2, page 97; also 10, 12, and 17, page 203. Aphakia Aphakia ('A priv, ^ukoq lens) is the name given by Bonders to that condition of the eye in which the lens is absent. There are several causes, by far the most frequent being one of the various operations for cata- ract, extractions, needle operations, &c. Besides these, aphakia may be caused by dislocation of the lens from injury, or may occur spontaneously, the latter being probably the cause of congenital cases where no lens can be seen. Aphakia necessarily converts the eye into a very hypermetropic one. The length of the eyeball which would be required (the curvature of the cornea being normal and the lens absent) to bring parallel rays to a focus on the retina is 30 mm., whereas normally the antero-posterior diameter of the eyeball is only about 23 mm. To test aphakia ; when a bright flame is held in front of and a little to one side of a normal eye, three images of the flame are formed, one erect on the cornea, another erect on the anterior surface of the lens, and a third inverted, and formed on the posterior surface of the