In so vast a field, and in one so new as regards ophthalmoscopic appearances, there remains still much to be accomplished. Useful knowledge has accumulated slowly, but numerous enigmatical appearances have been referred to their true causes, while many which at first sight seemed important have been proved to be either anomalies of formation or to have no pathological import. A complete and accurate description of all the eye symptoms in all diseases is an herculean task, because it presupposes the careful study of vast numbers of cases in every department of medicine: it is therefore out of the question for any one man to complete such a description from his individual efforts, and he must either remain content with a mere sketch or collate the combined experiences of many observers in different fields in order that it may be in any way reasonably perfect. To keep such an article within any moderate limits it has been necessary to condense much, and to consider only those points which the combined testimony of many observers shows to be important and of frequent occurrence. For similar reasons the writer has abstained from giving a complete list of all authorities treating of the subjects herein discussed, and has referred only to those which appeared to him to be some of the most important. Those readers who wish a more complete bibliography can readily obtain it by referring to the various monographs hereinafter quoted, and also by consulting the well-known essays of Foerster,1 Robin,2 and of Mauthner,3 or the treatises of Albutt4 and of Gowers.5
1 "Beziehungen der Allgemein-Leiden und Organ-Erkrankungen zu Veränderungen und Krankheiten des Sehorgans," in Graefe und Saemisch's Handbuch der Augenheilkunde, Bd. vii., 1877.
2 Des Troubles oculaires dans les Maladies de l'Encephale, Paris, 1880.
3 Lehrbuch der Ophthalmoscopie, Vienna, 1868, and Gehirn und Auge, Wiesbaden, 1881.
4 On the Use of the Ophthalmoscope, London, 1871.
5 Medical Ophthalmoscopy, London, 1879.
Such an article is necessarily a chapter on symptomatology, giving the eye symptoms in various diseases and pathological conditions, and the reader will therefore look in vain in it for any directions as to the treatment of such maladies, or for formulæ showing advantageous modes of administering medicines. The writer has intended, by describing and grouping eye symptoms, to enable the practitioner more readily to diagnosticate the various pathological conditions of other parts of the economy. The reader should look for a description of treatment in the various articles of this work which are devoted to the discussion of such diseases and morbid states. Local diseases of the eye, except so far as they are manifestly related to or caused by general disease, have been avoided in this paper, these topics being appropriate to a treatise on the diseases of the eye.
Changes in the Eye-ground and its Appendages due to Diseases of the Circulatory Apparatus—Heart, Blood-vessels, and Blood.
The ophthalmoscope has laid bare to our view a living nerve of special sense, the highly-developed end-organ in which it terminates, and the blood-columns circulating in them. In no other part of the body has Nature vouchsafed to us so clear an insight into her mysteries. In a state of health the index of refraction of the walls of the retinal blood-vessels is so nearly coincident with that of the surrounding media that they either entirely escape our observation or are only slightly indicated, thus allowing us to see only the blood-columns which circulate within them. Owing to the distance from the heart and to the restraining influence of the intraocular pressure, as well as to the minute size of the vessels in question, the pulse-wave has so far died out as to be ordinarily invisible, even by the aid of the eye-lenses which Nature has so kindly placed as magnifying-glasses to assist us in the study of intraocular phenomena. Even where we avail ourselves of the upright image in examining the normal eye-ground, by which an amplifying power of seven to fifteen diameters is obtained, we cannot usually detect any pulsation in the vessels, although exceptionally we may observe pulsation which is always venous and confined to the larger twigs of the venæ centrales as they pass over the disc and dip into the nerve-substance. By slight pressure on the eyeball with the finger venous pulse can always be produced. This phenomenon consists of an emptying of the vein from the optic pylorus toward the periphery, followed by a rush of return blood in an opposite direction, which takes place in eyes where the intravenous and intraocular pressures are nearly balanced. Under these circumstances the injection of a fresh quantity of arterial blood into the eye causes a temporary increase of intraocular pressure, which is transmitted through the vitreous to the main trunks of the veins, compressing them at the point nearest the heart (where the intravenous pressure is least) before the column of entering blood which has been hindered by the capillary resistance has had time to flow around to re-establish the current. Stronger pressure on the eye will produce an arterial pulsation by causing the intraocular pressure to become so high that the blood enters only during the systole of the heart and diastole of the arteries. This is not infrequently seen in glaucoma, where there is an augmentation of the intraocular pressure, but is never visible in the normal eye of a healthy individual. It should be kept in mind that the venous pulse often produces a slight change in the adjacent arteries which ought not be mistaken for arterial pulsation.6 Wadsworth and Putnam7 describe an intermittent variation in the size of the retinal veins independent of the pulsation produced by the heart's action, and having a period of about five respirations, analogous to the variation of arterial tension found in animals. Besides the arterial pulse already alluded to, produced by augmented intraocular tension, where the normal force of the circulation is not sufficient to drive the blood in a continuous stream into the tense eyeball, we have an analogous condition where the intraocular tension may be normal, but the arterial tension is diminished, and a full stream of blood can enter only during the diastole of the arteries or maximum of intravascular pressure. We may notice examples of this in insufficiency of the aortic valves, and in some very rare cases described by Quincke8 and Becker,9 who found it accompanied by an alternate flushing and pallor of the optic disc analogous to the capillary pulse which may at times be observed in the finger-nail under similar conditions of the general circulation. The arterial pulse may also accompany any cause which permanently or temporarily reduces the blood-pressure in the arterial system, such as pressure of a tumor on the ophthalmic artery or of a swollen nerve on the central retinal artery (as in neuritis): or, again, by feeble impulse of the heart, as in cases of fainting or in degeneration and dilatation of the walls of the blood-vessels.10 Becker relates11 a case of arterial pulsation in a left eye, supposed to be due to aneurism of the aorta at a point where the left carotid is given off, whilst the other eye presented the usual appearance of healthy retinal circulation: an aneurism at the origin of the innominate might reverse this and give arterial pulsation in the right eye. Usually, the pulse-phenomena in the retina are confined to the vessels on the optic disc and its immediate vicinity, but both Jaeger12 and Becker13 give cases where it was visible over the entire eye-ground. In cases of congenital malformation of the heart with cyanosis, such as defective closure of the foramen ovale or stenosis of the pulmonary artery, the retinal vessels show markedly the general distension of the veins and the change of color of the blood. Liebreich14 gives a striking picture of such a case, and Leber15 remarks that in two cases observed by him the dilatation affected the arteries as well as the veins. Knapp16 describes a case of swelling of the discs, with a vast number of thickened arteries and veins which radiated from them, many twigs reaching the fovea centralis. The autopsy showed general enlargement and hypertrophy of the whole vascular system without disease of the heart. Arcus senilis is often an accompaniment of fatty heart and an indication of extensive fatty degeneration of other tissues of the body, such as the small arteries of the brain and the recti muscles of the eye.17
6 For a minute study of the phenomenon, vide Jaeger, Med. Zeitschrift, 1854. See also his Ergebnisse des Untersuchung mit dem Augenspiegel, etc., 1876, pp. 60, 61. See also Becker, Arch. f. Oph., vol. xviii., part 1, p. 270.