CAUSES.- It is impossible to differentiate the various forms of neuritis from the cause for, while papillitis often indicates a cerebral or intra-cranial disease, still a neuro-retinitis may originate from similar conditions. If the neuritis is monolateral the cause is probably of local origin, depending upon some disease in the orbital region as caries periostitis, tumors and cellulitis or of some disease of the surrounding structures, such as the frontal sinus or the antrum of Highmore. If bilateral, it is in the majority of instances due to some diseased condition of the brain,. of which tumors (syphiloma, tubercle, glioma, and abscess) are by far the most frequent cause. Neuritis resulting from tumor of the brain is usually the most intense kind (choked disc) and does not seem to depend up their size of location, although tumors involving the cerebellum are considered the most apt to cause this lesion, while those of the convexity of the brain are least liable to cause optic neuritis. Next to cerebral tumors, tubercular meningitis is the most frequent cause. In addition to these local and cerebral causes we may find neuritis appearing in constitutional disturbances various kinds among which may be mentioned syphilis. Horstmann Archiv. Ophthal., vol. xviii., 2, 1889. gives the description together with the field of vision in eight cases of specific optic neuritis. It may also be found in severe febrile diseases such as typhus, variola, etc., from toxic agents, such as lead, albuminuria, etc.; in anaemia, especially when occurring in youth; in females with menstrual disturbances; from simple exposure to cold and rheumatism. It occurs in all ages and may be congenital. Several cases of optic neuritis have been found accompanying acute myelitis which was located in the lower and middle portion of the cord. The course. The course of the extension in these cases has not been demonstrated, but in all probability takes place along the fibres of the optic tract which have been traced to the posterior columns of the cord.
The method by which an intra-cranial disease causes neuritis optica has been the subject of much research and controversy. We believe the weight of opinion to-day has abandoned the earlier theories and accepts now what might be called two methods of extension, the mechanical and the inflammatory. In the mechanical it is due to hydrops of the sheath resulting from increased pressure within the skull, forcing the cerebro-spinal fluid forward between the sheaths of the optic nerve, causing through compression on the nerve an oedema and neuritis. In the inflammatory theory which seems to be supplanting the mechanical there is found evidence of inflammation in the nerve and its membranes, and even in the nerve head and retina itself. The assumption is that germs or some chemically acting material is carried from the brain to the papilla by the lymph current where its destructive influence is developed.
PROGNOSIS.- This depends chiefly upon the cause and severity of the disease. In all cases of neuritis optica the prognosis should always be guarded, as more or less loss of vision is apt to result from atrophy of the optic nerve. If due to some grave cerebral or general disease it is of course unfavorable; but, if there is no incurable disease causing the optic nerve lesion, then the eye trouble may be relieved. The progress of the neuritis is indicated as already mentioned by the progress of the visual and color sense. In neuritis from meningitis or cerebro- spinal meningitis useful vision may sometimes be recovered, especially if the primary disease is rapidly controlled or when the optic nerve has become involved only in the later stages of the disease; but, as a rule, however, more or less atrophy ensues. When the neuritis is due to orbital affections, syphilis, anaemia or menstrual disturbances, the prognosis is somewhat more favorable, as restoration of vision may be more or less complete.
TREATMENT.-As neuritis usually is associated with other and more serious diseases, the treatment will, as a rule, be directed to the general condition or cause of the neuritis. If resulting from some orbital condition, as cellulitis, tumors, etc., treatment as laid down under those headings would be indicated. In some cases of syphilitic neuritis the use of potassium iodide in large doses has given most flattering results. For remedies and their indications, what has been said under Retinitis applies to neuritis as well, but a careful study of the materia medica may show the true remedy to be one the least thought of.
Neuritis Retro-bulbaris.-(Axial Neuritis, Orbital Optic Neuritis, Central Amblyopia, Toxic Amblyopia). -This consists of an inflammation of the optic nerve between the eyeball and the chiasm and partakes of the nature of both a neuritis and an atrophy.
PATHOLOGY- The pathological changes in retro-bulbar neuritis have been the subject of extended investigation, and Samelsohn Graefe’s Archiv., 1882, No. I. was the first to describe in detail the anatomical changes in this disease. Since then his result have been corroborated by a number of others, among whom may be mentioned the cases of Vossius and Uthoff, reported at a later date in the same archives. More recent papers, to which liberal reference has been made in the preparation of this subject, are those of Knapp Plus Archiv. Ophthal., vol. xx., I, 1891. and De Schweinitz. (++) The Toxic Amblyopias, 1896. The disease is one of interstitial inflammation followed by atrophy of the axial fibres of the optic nerve, with connective tissue proliferation, which may start at different points. According to De Schweinitz there is an increase of nuclei, hypertrophy of the connective tissue and wasting of the nerve-fibres of a limited portion of the optic nerve known as the papillo-macular bundle; in fact, that there is an interstitial sclerosing inflammation comparable, according to Samelshon, to the same pathological process that alcohol produces in the liver. The papillo-macular bundle, according to Bunge consist of those fibres in the optic nerve which supply the retina, between the macula lutea and the papilla, and lie in the temporal portion of the nerve-tip in a wedge shaped segment. They occupy about one-third of the surface of the papilla with the apex of the triangle toward the vessels. These fibres gradually approach the axis of the nerve and reach it at the optic canal. In front of the chiasm they occupy the upper and inner portion, but in the optic tract they sink again to the central portion and remain there until they arrive at the brain. This same condition is the lesion in central amblyopia from alcoholism and other similar affections. A certain number of healthy nerve-fibres may be seen in the atrophic parts, which explains why sight may be preserved in isolated spots of the field in persons practically blind from retro-bulbar neuritis and also why they do not become perfectly blind in the amblyopia from alcohol.
SYMPTOMS.- Knapp divides the disease into acute and chronic types and details the following symptoms as found in acute retro-bulbar neuritis; More or less severe headache; pain in the orbit aggravated by movements of the eye and by pressure upon it; impairment of sight which advances rapidly and may cause blindness within day or two; central scotoma, for both color and form, which may be partial or complete, the periphery of the field remaining normal; diminished color- perception; moderate congestion and serous effusion of the optic papilla and surrounding retina, which may be followed by ischaemia, or this may be present from the beginning, and the termination of the condition, as shown by the ophthalmoscope, in either a return to the normal with recovery of vision, or partial atrophy of the disc-always in the temporal half-with a central scotoma remaining, or a general atrophy with total blindness.
CAUSES.-Exposure and over-work, acute infectious diseases, such as measles, rheumatism, diphtheria, etc., poisoning from alcohol, nicotine, lead, opium, etc., and suppression of menses.
PROGNOSIS is always uncertain, as many cases will either partially or completely recover, while others will result in permanent blindness, with sometimes the preservation of several islets of sight in the visual field, as already referred to.
In the chronic type, or what may, perhaps, be more properly termed toxic retro-bulbar neuritis, we find the following symptoms are presents.
SYMPTOMS.-There is a gradual loss of vision almost always affecting both eyes, the subjects frequently complaining of a fog before the eyes and that they see better at dusk, or day blindness; there is no pain, either spontaneous or upon pressure; central scotoma, stretching between the fixing point and the blind spot, at first for colors and then absolute; ring scotoma are sometimes noticed; the color- perception is lost for both red and green; and exceptionally for blue (green appears as a dirty white and red as a brownish color); the range of accommodation is diminished; the peripheral boundaries of the visual field are normal, and although direct vision is destroyed, complete blindness is not to be apprehended; the ophthalmoscopic appearances in the earlier stages of the disease may show a slight congestion or a nearly normal condition of the papilla, in the later stages an atrophy of the temporal half or sometimes the lower and outer quadrant of the disc or a general atrophy of the nerve.
Professor of Ophthalmology in the College of the New York Ophthalmic Hospital; Surgeon to the New York Ophthalmic Hospital. Visiting Oculist to the Laura Franklin Free Hospital for Children; Ex-President American Homoeopathic Ophthalmological, Otological and Laryngological Society. First Vice-President American Institute of Homoeopathy : President Homoeopathic Medical Society of the State of New York ; Editor Homoeopathic Eye. Ear and Throat Journal : Associate Editor. Department of Ophthalmology, North American Journal of Homoeopathy, etc.