Student's guide to diseases of the eye / by Edward Nettleship ; with a chapter on examination for color perception by William Thomson.

  • Nettleship, Edward, 1845-1913.
Date:
1883
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Licence: Public Domain Mark

Credit: Student's guide to diseases of the eye / by Edward Nettleship ; with a chapter on examination for color perception by William Thomson. Source: Wellcome Collection.

Provider: This material has been provided by the Francis A. Countway Library of Medicine, through the Medical Heritage Library. The original may be consulted at the Francis A. Countway Library of Medicine, Harvard Medical School.

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    CHAPTER XVI. AMBLYOPIA AND FUNCTIONAL DISOEDEES OF SIGHT. The term amblyopia means dulness of sight, but its use is generally restricted to cases of defective acuteness of sight (p. 43), short of blindness, in which the visible changes are disproportionately slight. Amaurosis indi- cates a more advanced affection—complete blindness with- ont apparent cause. These terms are essentially clinical, whilst papillitis and atrophy imply easily recognized patho- logical changes in the disk. Amblyopia may depend upon disease in the retina, in any part of the optic nerve or tract, or in the optic centres ; and it may be temporary or permanent. It is always most important to distinguish single from symmetrical cases. Two common and important forms of unsymmetrical amblyopia may be considered first. (1) Amblyopia from suppression of the image in one eye, in cases of squint. A squinting person, in order to avoid the difficulties of double vision (p. 33), suppresses the consciousness of the image formed in the squinting eye. If this process be continued, the sensorium becomes perma- nently blunted for images in this eye ; we say that the eye is amblyopic when we ought to say that the corresponding, centre loses perception. This defect, though often very great, affects only that part of the visual field which is common to both eyes, and is therefore least marked in the outer part of the field. It continues after the squint has disappeared, i. e., when both eyes are again directed con- stantly to the same object; but it can be relieved or cured,