A manual of diseases of the eye / by Charles H. May and Claud Worth.

  • May, Charles Henry, 1861-1943.
Date:
1924
Catalogue details

Licence: Public Domain Mark

Credit: A manual of diseases of the eye / by Charles H. May and Claud Worth. Source: Wellcome Collection.

    362/524 (page 306)
    The Determination of the Refraction by the Acuteness of Vision with Test-Types and Lenses. The Subjective Method. After having determined the acuteness of vision for distance as described on p. 9, we endeavour to ascertain which lenses are necessary to correct any error of refraction, and to bring the vision up to the normal The patient is placed in front of the test-types, which must be well illuminated by daylight or artificial light, at a distance of 6 metres. The trial frame (Fig. 26 j) is worn by the patient, and the left eye excluded by means of a solid metal disc. After testing the right eye we proceed with the left. If the patient reads £ without a glass he is probably either emmetropic or has hypermetropia. With bright illumination and contracted pupils an intelligent patient may be able to read even though he have myopia or astigmatism of 0-5 D. A weak convex spherical lens ( + 0-50 D. Sph.) is held in front of the eye; if he is easily able to read the line he has hyper¬ metropia, and the strongest convex spherical lens with which he can read f is the measure of his manifest hypermetropia. Even though he accepts a convex spherical lens, this is prob¬ ably not the measure of his total hypermetropia, which can