Manual of instructions for the guidance of army surgeons in testing the range and quality of vision of recruits and in distinguishing the causes of defective vision in soldiers / by T. Longmore.
- Date:
- 1875
Licence: Public Domain Mark
Credit: Manual of instructions for the guidance of army surgeons in testing the range and quality of vision of recruits and in distinguishing the causes of defective vision in soldiers / by T. Longmore. Source: Wellcome Collection.
Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.
65/148 page 51
![exhaustion of nervous power from over-stimulation by the bright light of the tropical day and the reflected glare from the water of the ocean, unrelieved by the variety of shade and colour which are met with on laud, and the consequent inabi]ity to perceive objects illuminated by the comparatively weak rays of moonlight. Snow-blindness appears to be of the same nature. The impair- ment of sensibility of the retina will be proportionably increased if cu'cumstances have induced any scorbutic taint or marked debility in the constitutions of the individuals affected. This description refers to simple functional hemeralopia; care must be taken not to mistake it for the diminished visual power which co-exists with retinitis pigmentosa, atrophy, and other structural changes of a grave nature in the retina. (b.) Nyctalopia, which is sometimes used as synonymous with night-bHndness, really signifies the converse condition of heme- ralopia, or that the patient can see better at night than he can during the daytime. In this state the weakness of the retina con- sists in its being unable to bear the stimulus of bright light from hyperesthesia. The normal acuteness of vision may not be mate- rially lowered in subdued light; but attempts to read print of moderate size, or to examine objects in bright daylight, produce all the symptoms of severe photophobia—ocular pain and dazzling, lachrymation, spasm of the eyelids, supraorbital pain, and general distress. After sundown, or when the eyes are shaded by tinted glasses, the patient moves about with comparative comfort, and sees objects clearly that he could not distinguish in ordinary day- Kght. The intolerance to the bright light thrown on the retina by the ophthalmoscopic speculum sufficiently indicates the presence of this abnormal irritabUity ; often too in eyes where there have been no previous symptoms indicative of inflammatory action, and in which the fundus seems to be quite free from inflammatory effects. Such cases are occasionally met with among the soldiers who are invalided during the summer for impaired vision from India. In these instances the affection seems to be due to the effects of tropical glare upon an oversensitively organised retina, generally associated, however, with a lowered state of constitutional tone. (c.) Hemiopia. Half-vision.—Impairment or loss of retinal perception, limited to the outer half of one eye and the inner half of the other eye. A recollection of the manner in which](https://iiif.wellcomecollection.org/image/b21932463_0067.jp2/full/800%2C/0/default.jpg)
