Persons affected with achromatopsy not only see well in deep gloom, but their vision of distant objects is particularly sharp, from the azure blue of the atmosphere presenting the strongest possible contrast to black. One intelIgent person sayst, " So much is this the case with me when viewing a distant object as to overcome the effect of perspective ; and the shading in the form and garments of persons at a distance is often so predominant as to overcome the effect of diminution in size ; and although, I see the object most dis tinctly, I an: unable to tell whether it he a child near me or a full-grown person at a distance." Daltonians endeavour to obviate the an noyances arising from their infirmity by taking some standard colours or shades as points of comparison, as for instance the green of grass ; they also bring the sense of touch to their assistance, and are enabled by these means, united with close attention, to avoid many errors ; but nevertheless they feel repugnance to express an opinion upon colours Aron-congenital Achromatopsy.—This though quite distinct from Clzrupsia, is generally a morbid symptom, and might easily be con founded with it. It is to be borne in mind that in certain cases of chrupsia objects ap pear tinged with colours foreign to them ; a general officer for instance saw all white objects of a deep orange colour at certain times of the day, and to a lady they appeared of a bright blue*; but in such cases all objects are tinged with a prevailing tint or it is confined to those which are white, coloured objects being properly recognised. In achromatopsy one or more colours are effaced, and the individual is no longer cog nizant of them.
Permanent Achromcdopsy. — A bootmaker in Paris f, was attacked with amaurotie amblyopia, which followed suppression of the cutaneous exhalation. It was accompanied with rheumatic pains, and there was at first irritation of the retina, but this subsided, leaving the sight imperfect. The patient, howeser, assured M. Szokalski that he had possessed a full perception of colours until after a copious bleeding from the MU. From that time he could only discern white, black, and grey, and could not distinguish an engrav ing from a coloured print. He one day bought a piece of yellow morocco leather by mistake for a white piece, and when examined by M. Szokalski, he could not distinguish any co loured patterns which were exhibited to him.
Dr. Mackenzie thus writes ; " I always con sidered this affection as a congenital one, till I was consulted by a man who had gradualiy become subject to it. He was by trade an ornamental painter, and could judge at one time perfectly of colours. His right eye was affected with mydriasis when he called upon me, and there was incomplete amaurosis of both eyes, so that he could no longer read a common type. On trying hint I found he mistook red and green. The use of spirits and tobacco was probably the cause of the affection of sight in this individual."T Wartmann # has related a case supposed not to have been congenital; this, however, is uncertain; the particulars are interesting, es pecially as valuable information, to which we have referred, was obtained from this patient.
M. Louis D — was the eldest of seven brothers and four sisters, who were assorted in a very singular category. The first set had red hair, and their vision was perfect ; the others had fair hair, and all were unable to distinguish colours. Louis D— belonged to the latter, as regards external appearances, but according to his own recollection, and the evidence of his mother, he perceived colours during his infancy, in the usual manner. At the age of nine years his skull was fractured, after which his perception of colours appears to have become defective. The fact however
of his brothers, who resembled him in ap pearance, being similarly affected from birth, weakens the chain of evidence on this point. His infirmity was for some time unknown, and his father endeavoured, by repeated cor poral punishment, to put a stop to what he called a perverse pretence, and a severe cor rection was administered by his master, a bookbinder, because he used red paper, in stead of green, for the covers of some books.
Temporary Achromalopsy. — This form ap pears to us not to have received the attention it merits, having been passed over in silence, or only cursorily alluded to, by the great majority of writers. The exciting causes are congestion, hepatic derangement, and dys pepsia, and it may exist in conjunction with more or less amaurois, or by itself, as a simple derangement of vision.
The first case we shall relate is highly in teresting from the marked manner in which the insensibility to colours existed, its dura tion and satisfactory disappearance as restora tion to health proceeded. It occurred in the practice of that very able physician, Dr. Hays.t Mary Bishop, mtat. twenty, was admitted into the Wills Hospital, Feb. 9, 1839. She was of short, robust stature, full habit, very dark complexion, black hair, and hazel irides, flushed face, colour of her cheeks at times almost of a purplish hue ; catamenia sup pressed. In 1837 and 1838 she had suffered from two attacks of cerebral disease ; after the first attack, objects appeared double. The second attack left her entirely blind, in which condition she continued for four months. After this her sight began to return, and at the period of her admission into the hospital, she could read- large print. When she came under the notice of Dr. Hays, in May, 1839, she had been largely depleted, and had taken remedies for the restoration of the catarnenia, under which treatment her sight had im proved. At this time it was discovered that she was unable to distinguish colours, yellow and blue being the only ones she could name with certainty. Nearly all others she termed brown, or hesitated to name, designating how ever their shades, or intensity of colour accu rately. Thus she called a deep red, dark brown ; a bright green,* light brown ; and very pale pink, very light shade of brown. The patient was not sensible at first that she laboured under any particular defect in distinguishing colours. She had noticed, that grass and roses did not appear as formerly, and she remembered that as her sight began to re turn, the first colour she perceived was yel low. The usual treatment for amenorrhea was adopted, and on the 29th of May the catamenia returned copiously, but continued only for a single day. It was followed, however, by a very marked improvement in vision. Roses now appeared to her of their natural colour, and site could distinguish the difference be tween the colour of the rose and that of the leaves, which she had not previously been able to do. By the middle of June she was able to see the eye of a needle and the end of a thread, but could not thread the needle from inability to see both at the same time. At this period she was again examined with the prismatic spectrum, and distinguished pretty accurately the yellow, blue, green, and red, hut was doubtful as to the orange. On the 30th of November it is stated that her sight was good, notwithstanding another attack of congestion and suppression of the menses. She distinguished all the primitive colours readily, and named most of the secondary ones as correctly as could be expected, with the exception of violet, which she was at a loss to name.