257 Nagel's Jahresbericht (Lit. 1873), p. 267.
258 Berliner klinische Wochenschrift, 1880, S. 169; Sitzung der Gesell. f. Psych. und Nervenkrankheiten, 10 März, 1879.
INJURIES OF THE FIFTH PAIR.—Although daily clinical experience shows us how promptly irritation of the sensitive branches of the trigeminus are followed by symptoms of reflex action in the eye—as, for instance, a cinder in the conjunctiva will cause contraction of the pupil, or a sharp pinch of the temple will at times cause pupillary dilatation—nevertheless, instances of impairment of the eyesight due to injury of the branches of the infraorbital or supraorbital nerves, and to this alone, are of rare occurrence. Sympathetic ophthalmia is the exception in which we too frequently see inflammation of one eye cause severe and often irreparable damage to its fellow. Scattered through ancient and modern surgical works there are many interesting and well-attested cases of impaired vision, some of which should be excluded on account of the want of proper evidence, which is now obtained from testing of the acuity and field of vision and ophthalmoscopic examination. Erichsen259 cites cases from Hippocrates, Fabricius Hildanus, and La Motte where amaurosis was produced by a wound of the brow. Chelius260 gives a case from similar injury, while Wardrop261 narrates three instances—one of wound of forehead, one from a blow on it with a ramrod, and one from an injury by a fragment of shell. The same author calls attention to the fact that amaurosis is more readily caused by wounds and injuries of the supraorbital and infraorbital nerves than from complete division of them. The various neurotomies and neurectomies performed upon the supraorbital branch since his day bear witness to the accuracy of his deduction. The same author quotes Morgagni as saying that Valsalva has seen amaurosis follow a wound of the lower lid which has been inflicted by the spur of a cock. Morgagni relates a similar case where the injury was inflicted by the broken glass from the windows of an upset carriage; and Beer reports a similar case of amaurosis from wound of the cheek. Guthrie262 remarks that "when the eye becomes amaurotic from a lesion of the first branch of the fifth pair of nerves, the pupil does not become dilated; the iris retains its usual action, although the retina may be insensible and the vision destroyed." More recently, Rondeau263 gives two cases, one of which caused lachrymation, photophobia, and eventual atrophy of the eye on the affected side, followed, fifteen years later, by loss of the fellow-eye from sympathetic ophthalmia, which had been produced by degenerative changes taking place in the shrunken bulb; and a second, in which a wound of the left brow became painful eight days after the receipt of the injury, and where pains became more severe as the wound cicatrized: in this latter case the left eye became foggy in three weeks, and soon sight was entirely lost, whilst six weeks after the accident there was dull pain in the right eye, with a sensation of cloudiness and a gradual development of photophobia in it. By local bloodletting, which caused the photophobia to rapidly yield, and a derivative and alterant treatment, the patient's right eye was so far improved that fifteen days later he could find his way about with the left eye, and could see to read with the right. Ophthalmoscopic examination showed in the left eye a serous swelling of the retina which entirely obscured the margin of the discs and gave the whole fundus a grayish tint, the veins being much enlarged and very tortuous. The right eye showed similar changes, though less developed.
259 Loc. cit., pp. 233-261.
260 South's translation of Chelius's System of Surgery, vol. i. p. 430.
261 Morbid Anatomy of the Human Eye, vol. ii. pp. 180, 181, London, 1818.
262 Quoted by White-Cooper, Injuries of the Eyes, London, 1859, p. 92.
263 Des Affections oculaires Reflexes, Paris, 1866, pp. 53, 54.
Affections of the Sixth Pair.
The extremely limited distribution of the sixth pair of cranial nerves renders the clinical study of their pathology comparatively simple. The eye supplied by the paralyzed muscle turns inward to an extent corresponding to the degree of loss of power in the paretic muscle plus the energy of its opponent rectus internus. The image of the object fixed by it falls, therefore, to the inner side of the macula lutea, and, being projected outward, causes a double vision, in which the image of the deviated eye appears to be in the temporal field of the affected eye (homonymous diplopia). When the healthy eye is covered and the patient endeavors to fix any near object with the paralyzed eye, it will be found that (as in all other cases of peripheral paralysis affecting any of the extra-ocular muscles) the secondary deviation of the sound eye is considerably greater than the primary deviation of the affected one; this being accounted for by the fact that the amount of consentaneous innervation which is sufficient to cause a small motion in the paretic muscle will produce a marked effect in the sound one.