(From Amaurosis 406 obscure). It is a decay or loss of sight, when no fault is observed in the eye, except that the pupil is somewhat enlarged and motionless. This disorder is styled a gutta sercna; cataracta nigra; offuscatio; caecitas minor; mydriasis. Some call it AmblyopŒia; q. v.

M. de St. Yves distinguishes this disease into the perfect and imperfect kinds. The perfect consists in total blindness; in the imperfect, there is at least a power of distinguishing light from darkness. There is a species which comes on instantaneously, continues for some hours, or days, returning often periodically in hysteria, etc. In another species, the pupil is always contracted, whether the unaffected eye is open or shut. In infants, the pupil is sometimes, though seldom, of its natural size, but no movement is observed in it, however exposed to the light. The nyctyalops is supposed to be a species of this complaint.

The causes are, a palsy in the retina, a tumour, or a plethora in the adjacent vessels; a translation of either a venereal or other poison. Suppressed periodical evacuations, vapours, hysteric and other nervous symptoms, sedative poisons, external injuries, or whatever intercepts the nervous influence in the eye, may produce this disease. In the middle of the optic nerve runs that branch of the carotid artery which enters into the eye; this artery, when distended, may press the nerve; render it paralytic, and cause the periodical species.

Dr. Cullen ranks this genus of disease in the class locales and order dysaesthesiae; and enumerates the species from the following causes, viz.. compression, debility and its causes, spasm, and the applications or the swallowing of poisons. The application of the bela-donna produces this disease.

On dissection, the optic nerve is sometimes found flaccid, and by far too small; in others it is compressed by extravasated blood, by a tumour, or by aturgescency of the artery which passes through it.

The phlegmatic, cachectic, aged, those with weak nerves, or that have been subjected to severities or excesses, and persons labouring under irregular or suppressed periodical discharges, are the principal subjects of this disorder.

The signs that indicate the presence of amaurosis are generally the blackness of the pupil of the eye, its size being larger or less than usual, and its not contracting nor dilating when exposed to a great degree of light. Its approach is generally attended with pain in the head; and as the pain decreases this disorder increases, though sometimes an absolute blindness comes on without any previous complaint. When it comes on without pain, and one eye only is diseased, no defect is discovered until the sound eye is closed; then the pupil of the diseased eye dilates, though exposed to a strong light; and when the other eye is opened it contracts to its natural size again. When it gradually comes on also, little specks appear on an object, or small flies seem to float before the eye, in the language of pathologists, muscae volitantes. In infants the pupil is sometimes of a natural size, though it hath no movement; and thus they continue during many months, before they can see. When pregnancy, suppressed periodical discharges, nervous disorders, or vapours, are the cause, a head-ach, vertigo, drowsiness, noise in the ears, etc. often usher in this disorder: in these cases it frequently returns, but soon spontaneously passes away.

The prognostics are generally unfavourable: if this blindness succeeds a fever, comes on in the aged or very infirm, a cure is not to be expected; if one eye fails, the other soon follows; but if the case is slight, the habit of body robust, if it happens after the measles or the small-pox, or about the age of puberty, it is sometimes cured.

The treatment of amaurosis is not often successful. It is easy to draw indications from the causes; but when it proceeds from plethora, sanguine or serous, bleeding or purgatives have equally failed. In this exquisitely-tender organ, palsy is apparently induced before the evacuations can relieve the oppression. Of internal remedies, valerian, castor, and the whole tribe of antispasmodics,have been most successful; but these should probably be confined to cases where it is connected with hysteria, and in these the disease often spontaneously disappears. The internal use of mercury has been recommended, but we have never found it efficacious. Active emetics have often succeeded, apparently from the general shock given to the system; and we know not from what cause the vitriolated mercury (turbith mineral) seems most salutary. If the resolution or the constitution can bear these severe shocks twice a week, amaurosis may frequently be removed. Setons and blisters to the neck dono service; but when the blisters have been applied to the temples they seem to have been occasionally useful. Sternutatories have been employed, but, in our hands, with little success. The best is the turbith mineral, with about ten times the quantity of any mild powder. Electrical sparks drawn from the eye twice a day have proved highly beneficial; and the Galvanic influence, if rescued from the hands of quacks, promises considerable relief.

See Heister's Surgery, Hoffman's Med. Rat. Syst. St. Yves on the Diseases of the Eyes. Mead's Cautions and Precepts. London Med. Journal, ii. 10. Wallis's Sauvages' Nosology of the Eves, p. 151, etc. 271.

Amaurosis a Synchysi.

See Caligo pupillae.

Amaurosis a Myosi.