Complete Text (Part 10)

? Potassium and mercury to saturation continued over a period of from three months to one year, and the maintenance of the system in as good a state of health as is possible. Atropine may be instilled and rest enjoined. To what form of tumor is the retina subject ? G-lioma is almost the only form. It is a kind of sarcoma. This form of tumor may spring from any part of the retina. It grows slowly at first, but in its later stages increases in size very rapidly._ _ It occurs most frequently in children, and produces a peculiar condition which has been mistaken for purulent choroiditis. This is because of the reflex obtainable from throwing light into the pupil._ When glioma is present, if it has attained to any size, a yellow reflex is noticed which has been likened to the reflex from the eye of a cat. What is the treatment for glioma of the retina ? Since the disease is very malignant, it is necessary to remove the eye as early as the condition can be diagnosed. 76 THE EYE. Metastatic tumors appear in other organs in a large proportion of the cases. What is pseudo-glioma of the retina ? In the progress of chronic forms of cyclitis a dense membrane is some- times thrown out which covers the posterior part of the lens. This gives out a yellowish reflex, usually paler than the reflex obtained from an eye which is the seat of glioma. It is benign in nature, and the eye possess- ing it need not be removed for the purpose of saving the life of the patient. THE OPTIC NERVE. "What is the structure of the optic nerve ? The optic nerve has its origin from the optic commissure or chiasm, and receives its nerve-filaments from the brain by way of the optic tracts and chiasm. The optic tracts take their origin from the posterior por- tion of the optic thalamus, the anterior quadrigemina, and from the outer and inner geniculate bodies. They pass downward and forward, uniting with the opposite tract, forming the optic chiasm. The optic nerves pass from the chiasm through the optic foramina into the orbit to the posterior part of the eye. They are surrounded by a sheath which is a prolongation of the dura mater of the brain. About 14 mm. back of the globe the nerve is pierced by a canal which gives passage to the large vessels of the retina, the central artery, and central vein. The fibres of the optic nerve are arranged in bundles which are separated from each other by connective-tissue trabeculae in which very small vessels are found. The fibres are medullated, Jbut lose their medullary substance just before entering the e.ye. At the lamina cribrosa the optic nerve-fibres pass through the meshes to the surface of the retina, and are there distributed. The optic nerves measure about If mm. in diameter as they pass through lamina cribrosa and 4 to 5 mm. in diameter in the part posterior to the globe. To what diseases is the optic nerve subject? Inflammation of the optic nerve is the principal disease. It may, however, be the seat of tumors, and is subject to atrophy without any preceding inflammatory change. What are the causes and symptoms of optic neuritis (papillitis) ? The causes are usually extension of disease from the meninges of the brain ; it is also excited by tumor and abscess of the brain. It may be caused by tumor of the meninges and by inflammatory processes which originate external to the brain. Chief among the latter is the neuritis due to poisoning from alcohol and tobacco. The external symptoms of neuritis are confined almost entirely to a diminution in vision. The ophthalmoscope must be used to diagnose the disease. On examining the optic disk with the ophthalmoscope we find that the edges have become blurred, often being entirely hidden. THE OPTIC NERVE. 77 The tissues are congested and raised, the elevation as determined by the ophthalmoscope often reaching from 1 to 2 mm. The central artery is usually slightly diminished in size, the veins enlarged and tortuous, and hemorrhages are frequently scattered over the surface of the disk and the retina in its immediate vicinity. The margin of the disk has a striped, woolly appearance, and because of the undoubted compression on the vessels it is known as choked disk. This condition reaches its highest development in infection from brain processes, as from meningitis, brain tumor, and abscess. The vision may be greatly impaired or may remain comparatively good for some time with a high degree of papillitis. What is the course of optic neuritis ? It usually runs a chronic course. In the acute cases accompanying meningitis, tumor, or abscess, or in high grades accompanying albumi- nuric retinitis, partial or complete atrophy of the optic nerve frequently results. In these pases vision is partly or completely abolished. In neuritis accompanying the use of alcohol or tobacco recovery with little loss of vision usually follows. What is the treatment of optic neuritis ? The treatment should be directed to the cause. The eye should be shaded and should not be used. Improvement of the general condition, with the administration of strychnine, and possibly the use of electricity in some cases, will aid in arriving at a favorable result. What is retrobulbar neuritis? It is a disease affecting the optic nerve, producing an inflammatory process which shows on examination with the ophthalmoscope only as an atrophy. Diminution in vision in certain parts of the field of vision is the first symptom noticed. What are the causes of retrobulbar neuritis ? Poisoning from alcohol and tobacco, injury, and la grippe are the principal causes. What are the symptoms in retrobulbar neuritis from alcohol and tobacco ? The patient comes on account of dimness of vision, and on exami- nation it is found that the central vision has fallen below the normal, while peripheral vision remains in the milder cases unimpaired. There is a central scotoma for red and green probably always present in this form of neuritis, and, while not pathognomonic, it is so seldom met with in other diseased conditions of the visual apparatus that it should always arouse suspicion of this as a cause of the disorder. In early cases the ophthalmoscope shows a slight degree of congestion of the optic disk, which never passes into a decided choked disk. If the case has existed for some months, there becomes apparent an abnormal paleness of the outer and lower quadrant of the optic disk. 78 THE EYE. What is the treatment of retrobulbar neuritis from alcohol and tobacco ? This consists in entirely stopping the use of alcohol and tobacco, and re- covery may be favorably influenced by medication to improve the general condition, and by the use of strychnine and the iodide of potassium. What are the causes of atrophy of the optic nerve ? Diseased processes in the brain affecting the cerebral centres of the optic nerve, optic neuritis, diseased processes occurring in the retina, as retinitis pigmentosa and albuminuric retinitis, traumatism, poisoning with lead, alcohol, and tobacco, and tabes dorsalis. Atrophy, originating in the central nervous system, is known as descending atrophy; orig- inating in the eye or in the nerve itself, as ascending atrophy. What are the symptoms of atrophy of the optic nerve ? No pain is experienced in this disease. The symptoms consist in a loss of vision, which is gradual and usually progresses by concentric limita- tion of the field. Examination with the ophthalmoscope discloses a pale disk, which becomes more white as the atrophy progresses. The paleness of the disk is due to an absence of the capillaries of the tissues of the disk. The central arteries become very much reduced in size, frequently disappearing almost entirely. The veins also are reduced in size. In atrophy that is not preceded by papillitis there is more or less shallow cupping of the disk, which begins at its margin, gradually sloping to the centre. This form of atrophy permits the trabecule of the lamina cribrosa to become visible throughout its entire extent. In atrophy pre- ceded by papillitis the disk presents an even white appearance, no cupping being present. The new-formed connective tissue which has developed at the time of the papillitis forms a cicatricial mass which fills in the disk. What is the treatment of optic atrophy ? The general condition of the patient should be improved as much as possible^ The cause, if* it can be determined, should be removed. Strychnine in gradually increasing doses is sometimes employed with benefit. Treatment is often of no avail. Does hemorrhage into the optic nerve-sheath occur? Rare instances of this condition have been observed. The symptoms are those of sudden diminution in vision. On exami- nation with the ophthalmoscope it frequently occurs that a small crescent- shaped hemorrhage may be seen partly encircling the disk at its margin. The prognosis in this condition is favorable, vision improving as the clot is absorbed. What interruptions to the blood-current in the central artery of the retina occur? Thrombosis and embolism of the central artery or of its branches are the principal forms of interference. Embolism is relatively rare, and is occasioned by endarteritis, which favors the formation of clots, followed THE VISUAL FIELD, COLOR-BLINDNESS, ETC. 79 by partial or total obstruction. This condition accompanies general arte- rial sclerosis in elderly individuals. Embolism is much more frequent than thrombosis. It is most frequently met with in those suffering from endocarditis, and a few cases are observed during recovery from the puerperal state. The plugging usually takes place at the point of the first division in the artery, just below the lamina cribrosa. The small plug may advance beyond this point, and affect only a branch of the central artery after it has passed on to the disk. What are the symptoms of thrombosis or embolism of the cen- tral artery of the retina? Rapidly-diminishing vision, gradually deepening, is characteristic of thrombosis. Immediate and total loss of vision is the result of embol- ism. Both are unaccompanied with pain. Examination with the oph- thalmoscope in recent total occlusion of the artery gives almost a niilky- white appearance of the fundus in the immediate vicinity of the disk, which gradually fades at the periphery into the normal red reflex. This is due to the escape of the plasma of the blood into the nerve-fibre and superficial layers of the retina. The vessels are hidden. At the fovea centralis a cherry-red spot is always present, which is the result of the showing through of the blood-vessels of the choroid, the transparency of the retina at this point not being interfered with. What is the treatment of thrombosis or embolism of the central artery ? In many cases treatment is of no avail, but in a relatively large per- centage of the cases rather forcible massage performed by directing the patient to forcibly turn the eye inward or downward, and rubbing and otherwise manipulating the eye as far backward as possible, so as to pro- duce some disturbance in the condition of the parts at the optic-nerve entrance, may succeed in releasing the clot to such an extent that some blood may find its way into the arteries and supply nutrition to the starv- ing layers of the retina in time to preserve some vision. In some cases the vision \vih rapidly increase to almost the normal. The result of such manipulation in embolism is liable to be much more beneficial than the same manipulation employed in thrombosis. Other forms of treatment are of little avail, and permanent loss of vision results. In cases where a branch only is occluded the field of vision is impaired in the portion corresponding to the area of the retina supplied with nutrition from the occluded branch. THE VISUAL FIELD. COLOR-BLINDNESS.— HEMIANOPSIA AND ITS VARIETIES. What is meant by the term visual field? It is the extent or space through which we are able to discern objects 80 THE EYE. with one eye alone or both together when directing the line of vision to one point. Each eye has a visual field peculiar to itself. The eyes have a visual field common to each other, and there is also what is known as the combined field of vision. The visual field of the right eye extends temporally 90° when the eye is fixed on an object directly in front. It extends 60° to the nasal side, 65° below and 55° above. The visual field of the left eye covers the same extent. The size of the field common to both eyes is 60° temporally on both sides, 55° above, 65° below. It is not perfectly circular, but is slightly contracted in the median line. The combined fields of vision reach to an angle of 90° on either side, 65° below, 55° above, and is notched in the centre, as is the common field. How is the field of vision determined ? It may be roughly and quickly determined by placing the patient with his back to the light, having him close one eye, and directing him to look Fig. 12. o N y tv5 ^^Zi ■-^^T ^ ' * / — w\ / /A 8 0 TO r ' / 1 / '/ 0| SO 4 / / y& ' 1 1 \Xft li I i 1{ 1 IX 1 1 ' i \ i ft \ \ . V^-J / / h V \ /\v / III 1 b y / ' r ll X '\^ . XVjT^ #/ v\ /^T5 !l^--^-< >^-^ / X V. v J?- >y **': y\ jtf 135 <^^4 ^- ** G s"s£ 8 0 ' Field of Vision of Right Eye, as projected by the patient on the inner surface of a hemisphere, the pole of which forms the object of regard (half-diagrammatic) : T, temporal, N, nasal side. W, boundary for white; B, for blue ; R, for red ; G, for green (Landolt). at your own corresponding eye, which should be about 1 foot in front of the patient. The hand may then be approached midway between the pa- tient and yourself toward the line of fixation, and a slight movement of THE VISUAL FIELD, COLOR-BLINDNESS. 81 the fingers be made. If the field of vision is normal, the patient should be able to detect the approach of the fingers toward the line of fixation as soon as you can yourself see them. This is a comparative test, and is very useful in the rapid approximate determination of the extent of the field. Accurate charts of the field of vision may be obtained by meas- urements made with any one of the perimeters now in use. That of Priestly Smith or the one made by Meyrowitz will be found to serve the purpose admirably. They are supplied with charts on which the extent of the normal field of vision is marked. What is the extent of the visual fields for colors ? The extent is considerably smaller than for white, and of the four principal colors, blue, yellow, red, and green, is about as follows: For blue, 90° toward the temple, 55° nasally, 55° above, and 65° below ; for yellow, very slightly smaller ; for red, 80° to the temple, 40° nasally, 40° above, and 50° below ; for green, 75° to the temple, 25° nasally, 35° above, and 45° below. Of what value is the visual field in the determination of dis- eased conditions of the visual apparatus ? It enables us to detect the influence of disease-processes on the vision and to locate in certain forms of disease the position of the lesion. It gives valuable information of the condition in cases of atrophy of the optic nerve and retina, and valuable suggestions regarding the time and propriety for operation in glaucoma. What are scotomata? They are defects in the visual fields, and may be total or relative. Total scotoma is where the vision is entirely abolished over the area of the defect. Relative scotoma is blindness for certain colors only. There is a normal scotoma, or blind spot, in the visual field of each eye which corresponds to the optic-nerve entrance. This is situated a little to the inner side of the point of fixation and slightly below the horizontal me- ridian. Certain diseases produce characteristic scotomata. In gradual atrophy of the nerve the scotoma is concentric ; in alcoholic amblyopia the scotoma is central and is relative ; in glaucoma the scotoma is con- centric, but greatest on the nasal side, and is absolute. In affections of the cortex of the brain it includes usually one-half of the field of vision of both eyes and on opposite sides. The latter is termed hemianopsia. What is color-blindness? Color-blindness is an inability to distinguish between certain shades of color. It is usually confined to an inability to recognize greens and reds. Very few cases of total color-blindness have been seen. How is color-blindness detected? The test usually applied is that of Holmgren's wools. These are 6— Eye. THE EYE. skeins of worsted of different tints of all the principal colors. The test is usually made by handing the patient a skein of one of the colors of which the tint is very decided, requesting him to pick out all the tints of this color in the collection. If color-blindness is present, the patient fails to recognize the different shades of the same color, the failure usually being in the reds and greens. The reds are usually mixed with the browns, the greens with the skeins of lighter color. Of what significance is color-blindness ? It renders the patient unfit for service where signals of different colors are employed, such as railway, navigation, and general signal service. What are the various forms of hemianopsia ? This