GEN. I. Paropsis lucifuga. Night sight. Treatment accidental causes, the extent of the expansion, they are able to see much better than mankind in the dark. Owls, bats, cockroaches, mothes, sphinxes, and many other insects, have a similar power. Where the disease proceeds from an accidental irriwhen from tability of the retina, sedative applications, as the tincture of belladonna, and internal sedatives, as hyoscyamus and conium, have often proved serviceable, and the more so when combined with the bark. In old age, or an early deficiency of the black pigment that covers the choroid tunic, medicine has very little chance of success, and all we can hope for is to afford occasional relief by palliatives, if the irritation be violent, or accompanied with inflammatory symptoms. when from defective pigment. GEN. I. SPEC. II. Endemic in various regions. Ordinary cause. Peculiarly SPECIES II. PAROPSIS NOCTIFUGA. Day-Sight. VISION DULL AND CONFUSED IN THE DARK: BUT CLEAR THIS species, the nyctalopia of neoteric authors, is said to be endemic in Poland, the West Indies, Brazils, and the intertropical regions generally*. Its cause is precisely the reverse of that of the preceding species; and proceeds from too great, instead of too small, an habitual exposure to light, whence the retina becomes torpid, and requires a strong stimulus to raise it. At noon-tide, therefore, it is sensible to the impressions of objects; but does not clearly discern them in the shade or towards the close of day. Day-sight is also said, in a work of allowed authofrequent in rity, to be endemic in some parts of France; and par some parts of France: Hantesierck, Recueil d' Observations de Médicine, 1. ii. † Mem. de la Société Royale de Méd. 1786. GEN. I. SPEC. II. ticularly in the neighbourhood of Roche Guyon on the banks of the Seine. And so general is its spread there, Paropsis that in one village, we are told, it affects one in twenty of noctifuga. the inhabitants, and in another, one in ten, every year. Day-sight. It makes its attack in the spring, and continues for three often returning pemonths sometimes, though in a slighter degree, return- riodically. ing in the autumn; and there are individuals who have had annual returns of the complaint for twenty years in succession. It passes off after having run its course, or Explained, rather, perhaps, after having been treated with due medical attention, without any inconvenience, excepting a weakness in a few eyes that renders them impatient of wind and strong light. The soil is here a dazzling chalk, and the keenness of the first reflected light, after the dreariness of the winter, is probably one cause of so general an evil. Perhaps, however, there is no part of the world in which this disease is found more commonly, Still more or more decidedly, than in Russia: but then it is rarely at times in commonly found except in the Russian summer, when the eye is Russia. exposed, almost without intermission, to the constant At what action of light, as the sun dips but little below the horizon, and there is scarcely any interval of darkness. The malady, again, mostly makes its appearance at this time among the peasants, who protract their hard labour in the fields from a very early to a very late hour; and at the same time exhaust and weaken themselves by their daily fatigue. The sight is soon restored by rest, a proper Easily shade, and bathing the eyes with an infusion of any bitter cured. and astringent vegetable. Dr. Guthrie, in the Memoirs Instance of of the Medical Society of London, from which this ac- its having nearly count has been taken, gives also an example of the disease led to exhaving appeared suddenly a few springs before in a de- tensive and tachment of Russian soldiers, who, being ordered to attack mischief. a Swedish post, at the moment of its incursion had nearly destroyed one another by mistake. These men had been harassed by long marches, and been exposed night and day to the piercing glare of an uninterrupted scene of snowy mountains, both which causes had concurred in producing this effect. season. serious GEN. I. SPEC. II. Paropsis noctifuga. Sir Gilbert Blane has found it occasionally occur in scorbutic patients; but no such disease appeared in the Russian soldiery. Hens are well known to labour under Day-sight this defect naturally; and hence they cannot see to pick up small grains in the dusk of the evening, and so employ this time in going to roost: on which account the disease is sometimes called hen-blindness. Amongst hens a natural defect; whence called henblindness. Curative process. When endemic mostly in termittent. Sight sometimes acute and vivid. Exemplified. Singular case of periodical day-sight. In this species tonics and gentle stimulants offer the best means of cure. The bark may be freely employed internally, and blisters externally, with the vapour of camphor, ether, or carbonated ammonia; and occasionally illining the ball of the eye with a few drops of the tincture of opium, the citrine ointment, or a minute portion of prussiate of iron, also in the form of an ointment. In most of the endemic cases it seems to be an intermittent, as the preceding species appear to be occasionally; and in such circumstances a free use of the bark is the plan chiefly to be depended upon. When the sight is once stimulated by the full light of the day, it occasionally becomes peculiarly acute and vivid. Plenck asserts that he has known some men labouring under this disease, evince so high an excitement of vision as to be able to distinguish the stars at noon. Dr. Heberden has communicated a singular case of this species which it will be best to give in his own words *. “A man, about thirty years old, had in the spring a tertian fever, for which he took too small a quantity of bark, so that the returns of it were weakened without being entirely removed. He therefore went into the cold bath, and after bathing twice he felt no more of his fever. Three days after this last fit, being then employed on board of a ship in the river, he observed, at sun-setting, that all objects began to look blue, which blueness gradually thickened into a cloud; and not long after he became so blind as hardly to perceive the light of a candle. The next morning about sun-rising his sight was restored as perfectly as ever. When the next night came on he lost his sight * Medical Transactions, Vol. I. GEN. I. SPEC. II. again in the same manner; and this continued for twelve days and nights. He then came ashore where the dis- Paropsis order of his eyes gradually abated, and in three days was noctifuga. Day-sight. entirely gone. A month after he went on board another ship, and after three days' stay in it the night-blindness returned as before, and lasted all the time of his remaining in the ship, which was nine nights. He then left the ship, and his blindness did not return while he was upon land. Some little time afterwards he went into another ship in which he continued for ten days, during which time the blindness returned only two nights, and never afterwards." As this distinguished writer has not undertaken to account for this singular affection, it may seem, perhaps, presumptuous to drop a hint upon the subject. Yet it should not pass unnoticed that the man was in a state of great nervous debility, and probably irritability, as its effect. He had formerly been employed, we are told, in lead-works, and had twice lost the use of his hands. And not many weeks from the time the above account closes, he complained of loss of appetite, weakness, shortness of breath, and a cough; which, together with other complaints, gradually increased upon him, so that he died before the end of the year. I have observed that nyctalopia noctifuga is often an intermittent affection. In the present case it was distinctly of this nature, and evinced a decided quotidian type. We are not acquainted with the exciting cause of this intermittent; but we know that when once a circuit of action has been established in a weakened and irritable habit, it adheres to the system with almost invincible tenacity, and is re-called with the utmost facility upon a repetition of such a cause. And hence the uniform return of the affection on ship-board where it commenced till a cure was obtained. Case ex plained. GEN. I. SPEC. III. Seat of affection chiefly the of the pre ceding two is the retina, SPECIES III. PAROPSIS LONGINQUA. Long-sight. VISION ONLY ACCURATE WHEN THE OBJECT IS FAR OFF. THIS is the dysopia proximorum of Cullen, the vuë longue of the French. 66 In both the preceding species the morbid affection seems chiefly to appertain to the retina; in the present iris, as that species it belongs chiefly to the iris, which is habitually dilated, and not easily stimulated to a contractile action. "For it is well known", observes Dr. Wells, to those who are conversant with the facts relating to human vision, that the eye in its relaxed state is fitted for distant objects, and that the seeing of near objects accurately is dependent upon muscular exertion". The species offers three varieties as follow: a Vulgaris. Common long-sight. 8 Paretica. Unalterable long-sight. 7 Senectutis. Long-sight of age. Iris relaxed, but moveable, cornea mostly too flat. Iris incontractile, pupil unchangeable, from partial paralysis. Cornea less convex; relaxa tion and hebetude common to all the powers of the eye. « P. longin- The FIRST VARIETY is common to every period of life, qua vulgaris, in which the iris is affected with an habitual relaxation ; Common long-sight. and may be sufficiently understood from the remarks already offered. B P. longin qua paretica. The SECOND VARIETY constitutes the disease called IMMUTABILITY OF SIGHT by Dr. Young*; and is ad Phil. Trans. Year 1793. |