about to lose his sight by cataract or by amaurosis. We may calm his fears on these heads, for with neither cataract nor amaurosis have these spectra any connection whatever. Even on the supposition that a gradual increase of the muscæ is to take place, not even the greatest possible accumulation of them can ever end in the production of an amaurosis, and much less of a cataract. It will be well, however, in any case in which the practitioner is consulted, to ascertain whether, independently of the muscæ, there be any symptoms of either of these two diseases present. The presence or absence of cataract we ascertain by the use of the catoptrical test, that is, by moving a lighted candle before the suspected eye, and observing whether the inverted image, formed by the reflection of the light by the posterior surface of the crystalline body, is distinct or not. If perfectly distinct, there is no cataract. We have no such simple or certain test of amaurosis. But if the pupil moves with its natural vivacity, and the patient is able to read a small type with the suspected eye, we may assure him it is not affected with amaurosis. A question, which the patient is very likely to put to us, is, whether the floating motes and threads which he sees are not liable to increase, and that to such a degree as at length to deprive him of sight. That they increase is true, although only very slowly, and never to such an extent as materially to interfere with vision. Even when the whole field of view presents entohyaloid spectra, the patient is still able to read, although, as he continues to do so, the muscæ sometimes gather together, so as to render portions of the page before him temporarily obscure. Very often they remain stationary for ten or twenty years, or increase by almost insensible degrees; and, although alarming at first, the patient gets habituated to them, and troubles himself no more about them. I believe the increase of myodesopia arises more from the eye becoming in a greater degree susceptible to the impressions of the bodies which cause this disease, than from any increase of the bodies themselves. This increasing susceptibility arises from over-use of the eyes, and from searching for and examining the muscæ too much. Sir David Brewster takes rather a gloomy view of the matter, when he tells us, that " it is quite possible that some of the cells near the retina and around the optic axis might be filled up with accumulated muscæ, and produce a considerable degree of blindness;" and that, "though these filaments have no morbid character, they may, nevertheless, obstruct and even destroy vision." The remark, that "these filaments have no morbid character," is founded, I presume, on the fact, that their existence may be detected in some degree by every eye, if recourse is had to the methods formerly (§ 12) described. Arriving, however, to such VOL. LXIV. No. 164. F a pitch as to attract notice as muscæ volitantes, they may fairly be considered as constituting a disease. If this disease consists in seeing the branches of the central artery of the retina, which advances through the vitreous humour towards the lens, or those which ramify over the external surface of the hyaloid membrane, the danger of their filling up any of the cells of the vitreous humour, or accumulating round the optic axis, so as to destroy vision, may be regarded as chimerical. If the corpuscles, which are seen, be an extravasation or deposition from the vessels, certainly we might conceive them accumulating more and more, till they proved a complete barrier to distinct vision; but experience gives no support to such an apprehension. Many authorities might be quoted to prove, that entohyaloid muscæ increase only with extreme slowness, or remain entirely stationary, and sometimes become even less perceptible. "I know many people who have complained to me of such things fifteen and twenty years ago, and who are still at this moment in the same state." Maître-Jan.* "These kinds of phantoms, which increase sometimes very slowly during the first five or six years, continue during the whole remainder of life without any kind of inconvenience. I know a great number of persons who have seen them thirty, forty years, and more, without their number or their figure having undergone the slightest change." Demours.+ "Twenty-five years after I had been first consulted in this case I again saw the patient. She then enjoyed good health and spirits. The motes were still occasionally perceived, but they had become so faint, that she could only see them in a strong light, and when she took pains to look for them. It ought, however, to be mentioned, that at this time her daughter was just married, whereas, when she first consulted me, she had lately lost her husband." Ware.‡ "Twelve years afterwards, I had occasion to see this gentleman again, when he informed me that he retained the perfect sight of both eyes, and could distinguish the most minute objects with either of them. In a bright light, however, he still perceived the motes as before, if he took pains to look for them; but he was now so much accustomed to their appearance, that they did not occasion any uneasiness." Ibid.§ "It is certainly for from twenty to thirty years that I have seen these same appearances," says Prevost, at the age of 50 ; and, at the age of 79, he adds, "Since, up to a very advanced • Traité des Maladies de l'Eil, p. 281. Troyes, 1711. + Traité des Maladies des Yeux, Tome iii. p. 421. Paris, 1818. Op. cit. p. 258. Ib. p. 260. age, I have enjoyed very good sight, I may support, by my case, the opinion of the oculists who reckon these appearances of small importance. 66 They are quite innocent in their nature, and exist in persons whose powers of vision are most acute. I have been subject to them from childhood." Müller.+ § 30. Treatment of entohyaloid muscæ. Entohyaloid or floating muscæ are not much under control, and are very seldom removed by medical applications. If of old standing, and not increasing, it is needless to interfere. When of recent origin, and the exciting cause evident, they are sometimes cured. The treatment most likely to be useful is as follows: 1. The patient must be put on his guard against the exciting causes, and carefully avoid them; such as, too much straining of the sight, excess of every sort, night-watching, the use of alcohol in any form or quantity, and the like. "The only means which often does good in this disease," says Walther," is rest of the eyes, and abstaining from every employment which strains the sight. I know patients who have got completely free of musca volitantes which they had seen for several years, by giving their eyes long-continued rest, which, however, again appeared, as soon as they wrought for some days, so as to strain their sight."+ 2. If the stomach is weak, and the bowels costive, a course of laxatives, followed by tonics, should be prescribed. To strengthen the constitution, and especially the nervous system, should by every likely means be attempted. This indication will best be answered by cinchona, steel, and the cold bath. Richter mentions the case of a lady, who was troubled with this disease after a difficult labour, and who was completely freed of it by the continued use of sulphuric ether. In another case, in which the digestion was much impaired, and the patient troubled with acid eructations, a mixture of ox-gall and assafoetida was of great use. § 3. A torpid state of the liver requires small doses of the blue pill, either by itself or combined with purgatives. I have known a gentle course of mercury successful in curing the disease, probably by its sorbefacient powers. Iodide of potassium, I have also found completely successful in removing muscæ volitantes of recent standing. 4. Where the symptoms of determination of blood to the head are well marked, venesection or arteriotomy, leeches to the head or cupping, and counter-irritation are indicated. Of twelve cases Op. cit. p. 247. + Elements of Physiology, translated by Baly, Vol. ii. p. 1214. London, 1842. Op. cit. p. 20. § Op. cit. 514. treated by Dr Schlagintweit, eight, we are told, were cured by solvent and derivative medicines, and by bleeding at the foot. DrWallace reports two cases, in which cupping was very beneficial.t 5. When muscæ appear dependent on disease of the heart, leeches are recommended by Mr Wardrop to be applied over this organ till its impulse is diminished. The fulfilment of this indication may be promoted by small doses of antimony and the use of laxatives. If the patient complains of cold feet, the warm pediluvium is to be used at bed-time; and it may be remarked, that this simple remedy is of great importance, where the disease is connected with a difficulty of obtaining sleep. An irritable state of the heart, remaining after its impulse is subdued, Mr Wardrop endeavours to remove by the exhibition of sulphate of iron. 6. Antispasmodics appear to have been chiefly confided in by Ware in the treatment of muscæ; such as, two or three times in the day a small dose of the volatile tincture of valerian, mixed with an equal quantity of tincture of castor, and joined occasionally with the camphor mixture, or with infusion of cascarilla. 7. Exercise in the open air, and a change of residence, with such occupations and amusements as are likely to withdraw the mind from any source of anxiety or distress, are found to be beneficial. A course of mineral waters has sometimes been successful, probably more from the change of scene, hilarity of mind, exercise of body, and regularity of habits, by which such a course is accompanied, than from the effects of the waters themselves. 8. If the eyes feel hot, heavy, or uncomfortable, they should be bathed with either some cold or some warm application, according as the patient feels the one or the other the more agreeable. Cold water, or a cold lotion, consisting of equal parts of water and the spiritus ætheris nitrosi, will answer in the one case; tepid water, or a tepid infusion of any aromatic herb in the other. Sponging the forehead, temples, and outside of the eyelids, morning and evening, with camphorated spirit of rosemary, eau de Cologne, or the like, is also to be recommended. 9. Rust, it seems, continued to recommend the practice of puncturing the cornea in cases of myodesopia, a plan originally proposed with the view of allowing the cause to escape out of the eye, and tried unsuccessfully by Demours; but which in Rust's hands was followed, we are told, by the vanishing of the muscæ. If it really was so, the operation probably acted in a similar way as it is known to do in cases of ophthalmia, by giving relief to the turges • Ammon's Zeitschrift für die Ophthalmologie, Vol. ii. p. 47. Dresden, 1832. + London Medical Gazette, Vol. xxiii. p. 110, London, 1839. Chelius' Handbuch der Augenheilkunde, Vol. i. p. 371. Stuttgart, 1843. cent state of the vessels. On one occasion, however, under the care of Dr Helmbrecht, the operation of puncturing the cornea, not merely cured the eye of myodesopia, but gave exit, we are told, to the efficient cause-a microscopic conferva, of the exact shape of the musca volitans previously seen by the patient !* IV. CIRCULATORY SPECTRUM. § 31. Vision of blood-corpuscles moving through vessels of the eye. When I look fixedly for a few minutes at the clear sky, I begin to perceive a multitude of lucid points, darting in every direction through the field of view. The motion of these points is real and altogether independent of any movement of the eyeball; and is so exactly like that of the circulation in the web of a frog's foot as seen with the aid of the microscope, that I have no doubt this spectrum is owing to the blood-corpuscles passing through the vessels either of the retina or of the choroid. On sneezing, coughing, yawning, or straining to evacuate the bowels, it is well known that the eyelids close instinctively, for the purpose of sustaining the eyeball, and preventing the bad effects which these forcible acts of expiration might otherwise have on the delicate textures within that organ, in consequence of the regurgitation of the blood through the veins. The pressure of the eyelids, as they close in these acts upon the eye, often produces a flash of light, similar to the sensation of a luminous spectrum which is experienced when the eyeball is pressed on one side with the finger. But if we happen to sneeze, cough, yawn, or strain with our eyes open, or rather chance to open our eyes during one or other of these acts, the circulatory spectrum becomes very evident, and continues for some seconds. Purkinje, in his description of what I conceive to be the circulatory spectrum, says, that the lucid points which spring up in the field of vision, without having changed their places, suddenly disappear, leaving behind them black points, which even as suddenly vanish. To my view the lucid points career, as if in pursuit of one another, with a motion, which, though rapid, can still be easily followed. The appearance of black points, succeeding the lucid ones, I have witnessed only after sneezing. Purkinje does not attribute the phenomena he describes under the title of aufspringende Lichtpünktchen," to the circulation of the blood, but to a conflict of contraction and expansion of the nervous substance. Müller, on the other hand, considers the appearances as evidently due to the motion of the blood, and re • Revue Ophthalmologique de l'Année 1842, p. 251. Bruxelles, 1843. + Beobachtungen und Versuche zur Physiologie der Sinne, Vol. i. p. 67. Prag' 1823. Op. cit. p. 1211. |