Defects of sight and hearing : their nature, causes, prevention, and general management / by T. Wharton Jones.

  • Thomas Wharton Jones
Date:
1859
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Licence: Public Domain Mark

Credit: Defects of sight and hearing : their nature, causes, prevention, and general management / by T. Wharton Jones. Source: Wellcome Collection.

Provider: This material has been provided by the National Library of Medicine (U.S.), through the Medical Heritage Library. The original may be consulted at the National Library of Medicine (U.S.)

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    im li IHT. rimple fixed Dilatation of the Pupil. The pnpi] is, in ordinary light, of its medium size, which i> about one fifth of an inch in diameter. When the light to which the eye is exposed is strong, the pupil becomes contracted toaamaller size; but, oo the contrary, when tho light is very dull, it is dilated to a larger sice. Dilatation of the pupil, persisting in opposition to the influences to which the pupil is ordinarily obedient, some- times occurs, unaccompanied by any other defeot of sight than may he accounted for bj BUCh a derangement of the optical adjustment of the eye. That the ease is of this Simple nature, and not one of that serious disease of the sight—amaurosis (of which dila- tation of the pupil is a pretty common Bymptom,) is ascer- tained if the patient, on looking through an aperture in a card of less than the ordinary size of the pupil, is able to bjecta quite distinctly. Not the lc>s however, should the patient take advice on hi.- case, for the dilatation is apt to persist, and the sight me more impaired. Myopia, or Short-rightedneu, Presbyopia, or Far-righted- nestf (le. When the distance at which an ordinary sized type can be read comfortably, is much less than twelve inches, the -id to lie myopic, or short ; when, on the contra- ry, it is much greater, vision is said to he presbyopic, or long. Preparatory to entering on an account of short-sighted- ncss and far-sightedness, it will he useful to make son,.' oh-