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Diseases Of The Optic Nerve

Diseases Of The Optic Nerve.

IN this section it is not proposed to discuss the affections commonly classed as amblyopias or amauroses, although in many of them the optic nerve is primarily or secondarily affected : they will be considered in another article (page 457), as will also many of the congenital peculiarities of the optic disk (pages 191 195).

Hyperemia of the Optic Nerve. A congestion of the optic nerve can only be diagnosed with any approach to accuracy when the intraocular end of the papilla is involved ; and the color of the normal papilla is subject to such wide variation in different individuals that a positive diagnosis of hyperemia, even where it is strongly suspected, is frequently difficult, unless the papilla has been previously examined under normal conditions or unless the nerve in question can be compared with that of the other side. It shows itself in a deepening of the normal, slightly rosy tint of the papilla, the larger vessels remaining unchanged, or, at most, the veins showing enlargement. Its diagnosis chiefly of value as a premonition of approaching inflammation or of inflammation already exists farther back in the nerve. It also occurs in many cases of choroiditis or with inflammation or irritation of the iris, cornea, or ciliary body. Where, in addition to a decided congestion, the outlines of the papilla become at all indistinct, it is preferable to speak of slight or incipient optic neuritis.

Optic Neuritis. Where an inflammation of the optic nerve is plainly revealed by the ophthalmoscope, it is commonly called papillitis, although in many cases the retro ocular portion of the nerve is also involved, sometimes very extensively.

Where from the severity of the disturbance of Vision in comparison with the negative or slightly pronounced character of the ophthalmoscopic symptoms an inflammation of the nerves between the eye and the chiasm is diagnosed, the condition is termed retro bulbar neuritis.

Papillitis, or Intraocular Optic Neuritis. Soon after the invention of the ophthalmoscope permitted intraocular lesions to be studied during life, v. Graefe was led to divide inflammations of the optic disk into two classes: papillitis from stasis (Stauungspapille), commonly called choked disk ' which he supposed to be due to edema and hyperemia of the disk from increased intracranial pressure; and descending neuritis, sometimes known as simple, optic neuritis, in which he believed that the inflammation spread down the nerve trunk from the intracranial lesion. The experience of subsequent years has shown that the lines between these two forms cannot be drawn sharply, either from a pathological or an etiological standpoint, although for practical purposes the distinction is a useful one.

Objective Symptoms. In its pronounced form choked disk is charac¬terized by entire obliteration of the outlines of the papilla, an elevated mass of tissue, marked on the surface by radiating strie which fade off gradually into the surrounding retina, taking its place ; near the center of this the larger retinal vessels appear, the veins being generally large and tortuous, while the arteries often are apparently reduced in size. On and close beneath the surface of the elevation may generally be seen numerous enlarged capillary vessels, while on its borders and in the surrounding retina small patches of whitish exudate and hemorrhages, often flame shaped, are not uncommon. Very rarely pulsation of the retinal arteries has been seen (Plate 6, Fig. I.).

When the hemorrhages and patches of exudate are large and numerous in proportion to the elevation of the disk, the condition is more often termed neuro retinitis, and in such cases opacities may develop in the posterior portion of the vitreous, sometimes with newly formed blood vessels leading out to them. The height of the elevation, measured with the ophthalmoscope, varies from I D. to 6 D. If it is less than this, the term choked disk hardly applies, and the condition verges into that of simple, papillitis, where, with less complete obliteration of the borders of the papilla, with much less strongly marked striation, hemorrhages and exudate may occur even more extensively than in cases of pronounced choked disk.

In some cases the condition of choked disk may persist with little change for months or even for a year or more, but sooner or later, if the patient lives, the elevation recedes ; the striation of the tissue becomes less marked; the hemorrhages and exudate if any existed, are absorbed ; and the outlines of the papilla begin to show dimly. With the continuation of this retrogressive process the picture generally changes to that of neuritic atrophy, to be described later on. In some cases, however, where the inflammation has not been very severe nor prolonged, the nerve may gradually assume an almost normal aspect.

Subjective Symptoms. While, in general, it may be said that in cases of choked disk the disturbance of vision increases with the evidence of stages in the papilla, this rule is subject to great exceptions. The vision of eyes presenting the same ophthalmoscopic picture is found to vary between the normal and complete blindness; occasionally marked choked disk persists for manv months without any perceptible impairment of sight. This fact and the Tact that the sight may be subject to sudden changes without any corresponding difference in the ophthalmoscopic picture suggest that much of the disturbance of vision may be due to accompanying retro bulbar or intracranial lesions. The occurrence of normal vision with marked choked disk, where the development of the papillitis is not too sudden, may be explained, as Leber suggests, on the ground that the nerve fibers may accustom themselves to the changed position and increased pressure without impairment of function.

Where, as is common, the sight is seriously interfered with in the course of the papillitis, there is generally a gradual reduction of the central acuity, sometimes with a central scotoma, more often with a contraction of the field at the periphery, and frequently more marked at the nasal side; but the mode in which the field of vision is interfered with is subject to all sorts of variations. The color sense necessarily suffers greatly in the severe cases, but if the amblyopia is not extreme it may be very little affected. Sometimes with marked peripheric contraction of the field for white the color limits in the remaining portion of the field may be normal. Disturbances of the normal relations of the color limits may be observed g. red in certain areas may be seen farther toward the periphery than blue.

Some patients complain of flashes of light and other subjective phenomena indicating irritation of the optic nerve fibers.

With the subsidence of the ophthalmoscopic symptoms an improvement of vision generally sets in, which will be considered more fully when treating of the Prognosis.

Pathology. Pathologically, the distinction between choked disk and descending or simple neuritis is found to be entirely arbitrary. In some cases in which, during life, there was a choked disk, postmortem examination reveals that the inflammation is limited almost entirely to the intraocular part of the nerve, with a distention of the intervaginal space by serous fluid as almost the only retro ocular symptom. In others there is marked, sometimes purulent, inflammation in the intervaginal space and the nerve sheaths, with very little affection of the nerve; while in still others the nerve trunk is the seat of an intense interstitial inflammation, and the intervaginal space and outer sheath are normal. Conversely, the ophthalmoscopic picture of simple neuritis or neuro retinitis may coexist with inflammation of the nervetrunk or with a normal nerve trunk and extensive hydrous or inflammation in the intervaginal space and its walls.

Microscopically, a choked disk in the early stages shows severe venous hyperemia, with some edema, although on account of post mortem changes the latter lesion is less marked than would be expected from the ophthalmoscopic appearance; and a marked swelling of the nerve fibers. Later, the tissues become infiltrated with leukocytes, and accumulations of these at points corresponding to the areas of whitish exudate seen during life are found to have undergone granular or fatty degeneration. Fresh hemorrhages are, of course, visible as such, while older ones are suggested by patches of pigment. Still later, the formation of new connective tissue becomes apparent, especially along the blood vessels, the walls of which are often much thickened. The nerve fibers atrophy to a greater or less extent, their place being taken by granules and minute fat like globules, which in their turn become absorbed (Fig. 263).

The changes in the retro ocular portion of the nerve trunk are mainly those of an interstitial neuritis, the septa of connective tissue being infiltrated with leukocytes and, later, thickened from new formation of connective tissue. From the resulting pressure, and perhaps from the direct influence of the ptomains, the nerve fibers, if the process continues long, undergo degenerative changes and atrophy. The degenerative changes in the nerve fibers, sometimes described as medullary neuritis, are probably, as Alt suggests, merely secondary to interstitial inflammation or to degeneration elsewhere.

Where, with the main lesion in the nerve head, the signs of inflammation extend into the nerve trunk for a short distance toward the brain, the condition is termed ascending neuritis In such cases edema of the nerve trunk has been frequently found. Besides the hydrops of the intervaginal space, which is so common, optic perineuritis often occurs in the form of more or less inflammation of the opposing surfaces of the pial and dural sheaths and of the arachnoidal framework between them. This may be slight, or so severe as eventually to obliterate the intervaginal space with a mass of new formed connective tissue.

Etiology. The most frequent cause of typical choked disk is the development of an intracranial tumor, some observers stating that it occurs in 95 per cent., of all cases of such tumors. The nature of the tumor seems to be of very little importance: it may occur with any of the neoplasms, whether of the brain substance, of the meninges, or of the bony walls, or with gummata, tubercles, cysts (whether of entozoic or other origin), abscesses, or aneurysms. Tumors of the cerebellum are especially apt to produce it.

The method in which brain tumors cause optic neuritis is a matter still in dispute. Von Graefe supposed that, owing to the increase of intracranial pressure, an abnormal amount of fluid was forced into the intervaginal space, and produced a stasis in the papilla which tended to become exaggerated on account of the unyielding nature of the walls of the channels through the lamina cribrosa. These acted, it was supposed, like the abdominal rings in a case of strangulated hernia, the pressure, naturally, having a greater effect upon the outflow through the yielding veins than upon the inflow through the stiffer walled arteries. This theory received considerable support from the observation of Manz and others, that in many cases of brain tumor there actually existed a distention of the intervaginal space with cerebro spinal fluid.

The other most widely accepted theory is that of Leber and Deutschmann, who hold that the optic neuritis in these cases is not merely a stasis, but is an active inflammation caused by the passage of irritating substances, produced either directly or indirectly by the tumor, from the cranial cavity down to the nerve bead. In favor of this view it may be said that, as a rule, a certain amount of meningitis can be demonstrated in the neighborhood of most brain-tumors , and that in many cases no hydrops of the intervaginal space can be found, but, on the contrary, a normal intervaginal space with marked interstitial inflammation of the nerve trunk. The alleged production of the symptoms of choked disk in animals by injections into the cranial cavity or into the vaginal space are Dot admitted as evidence by the supporters of the inflammation theory, on the ground that higher pressures were used than probably ever occur in the human being. The objection that typical choked disk is seldom observed in cases of acute meningitis is met by the suggestion that the slight neuritis which is often observed does occasionally develop into a choked disk if the patient lives long enough.

A careful review of all the available facts leads one to believe that while, in certain cases, the element of intracranial and intervaginal pressure plays an important part in the production of choked disk, in the majority of cases the latter depends upon an active inflammation.

In addition, there should be mentioned the theory of Parinaud, who holds that choked disk results from an extension, through the trunk of' the optic nerve to the papilla, of the interstitial edema of the brain tissue which is so commonly found in intracranial troubles. This edema of the nerve trunk is also recognized by Ulrich, but he holds that its effect's upon the papilla are produced not directly, but by compressing the central retinal vein.

The importance of optic neuritis as a symptom of brain tumor can be appreciated from the fact that, aside from its frequency, it is sometimes the first symptom to attract the notice of the patient; in fact, the progress of the tumor may be so slow that, as in a case reported by Leber, a slight optic neuritis may even pass over into atrophy without the knowledge of the patient, years before death occurs. The occurrence of a double choked disk, then, without other grounds for its explanation, is always sufficient reason for a strong suspicion of brain tumor. As a source of error in such cases, may be mentioned the unique case of Krohn, in which a double optic neuritis was caused by a small metastatic tumor from an ovarian carcinoma developing in the optic nerve immediately behind each globe.

In rare cases the optic neuritis accompanying brain tumor is one sided, and may even occur on the side opposite to the growth. This is explained by the supporters of the pressure theory of choked disk on the ground of a localized meningitis or hemorrhage.

Of extreme rarity also is the occurrence, in a ease of suspected brain-tumor, of a second attack of papillitis some time after the first has subsided. In the case of de Sehweinitz and A. Thomson the neuritis, headache, and epilepsy disappeared after a simple trephining, but all returned at the expiration of a year.

With reference to the diagnosis of brain tumor, it should not be forgotten that, occasionally, a tumor may cause a neuro retinitis precisely like that generally considered diagnostic of albuminuria.

the distinction between choked disk and simple or descending neuritis, it may be said that all tumors or inflammations within the cranial or orbital cavities may cause a papillitis; this naturally includes all the varieties of meningitis and infectious thrombosis of the brain sinuses.

Optic neuritis has also been observed in the greatest variety of infectious and other general diseases. It has been most commonly noticed in the course of measles, typhoid fever, and ‘la grippe," but it has also been mentioned in connection with scarlatina, variola, malaria, whooping cough, beriberi, pellagra, typhus, typhoid pneumonia, rheumatism, diphtheria, and myxedema. In some of these 'cases the neuritis is undoubtedly secondary to a nephritis ; in others, to a meningitis but there is no reason for supposing that some of them may not indicate an actual infection of the trunk or intervaginal space of the nerve, while still others may result simply from the general toxemia. Neuritis also occurs with various disorders of menstruation, generally with a sudden checking of the flow, and with premature menopause and atrophy of the uterus. The fact that in adults, as well as children, hydrocephalus internus may cause double sided neuritis is of importance, because, on account of the unyielding character of the skull, the diagnosis is much more difficult than in children, and the neuritis might be thought to confirm an erroneous diagnosis of brain tumor.

Optic neuritis has also been observed in various marked deformities of the skull, particularly in the high and narrow variety known by the Germans as “Thurmschadel ' (tower or steeple skull). A post mortem examination in one such case (Michel) showed signs of pachymeningitis, with marked hyperostosis of the skull bones, both optic foramina being decidedly narrowed. With multiple foci of cerebral softening the nerve has, in the early stages, been found to be inflamed, atrophy setting in later, though it seems probable that the hemorrhagic meningitis which often accompanies such cases is the more direct cause of the inflammation of the nerve.

With various other brain and spinal diseases, to be considered more fully in connection with atrophy of the nerve, a slight optic neuritis has been observed as a forerunner of the atrophy.

Syphilis may cause optic neuritis, either by attacking the nerve directly or by producing a gumma in the cranial cavity.

Whether the cases of neuritis which have been observed in the puerperal state have been due to a general infection, or whether they are more akin to the cases which Valude and Bull have reported, in which the optic nerve has been attacked in several successive pregnancies, apparently without any kidney complications, is uncertain. It is possible, also, that some of the' cases which have been described as neuritis during lactation may belong here, although others are more probably akin to the neuritis which has been observed in the course of chlorosis. The anemia produced by the too abundant or too long continued lactation, as well as that occurring in the chlorosis, produces neuritis, probably through hemorrhages resulting from malnutrition changes in the walls of the blood vessels. ln other cases the affection of the optic nerve has seemed to be due to a sudden checking of the flow of milk.

The neuritis which sometimes follows severe hemorrhages is also probably due to alterations in the blood vessel walls, the malnutrition caused by the extreme anemia so weakening the coats of the vessels that, when the blood current begins to resume its normal force, transudations and hemorrhages occur which may either give rise to the picture of optic neuritis directly, or possibly indirectly, through pressure in the intervaginal space. A striking case of this character is that reported by Lessner, in which three weeks after a severe postpartum hemorrhage the vision suddenly became affected, the difficulty progressing within three days to complete blindness; the ophthalmoscope revealed a marked choked disk in each eve. This was immediately followed by the onset of an ascending myelitis, which caused the death of the patient at the end of two weeks.

A cause of neuritis which has been insisted upon by Panas is gonorrhea, though, in the case which he reports, the connection between the urethral affection and the neuritis is less obvious than in the more recent ease of Campbell Highet. In Panas's case one eve remained blind, the other being scarcely affected, while in Campbell Highet's case the affection was onesided and ended in complete recovery.

In treating of the effects of nephritis I upon the eye the main stress is usually laid upon the retinitis, though, so far as the functional disturbance is concerned, the optic neuritis is probably of greater importance. The retinitis is much more apt to clear up without leaving permanent damage, if the nephritis is of the curable variety, than is the affection of the nerve. The writer has a case on band at present in which the retinitis has been cured for months, while the nerves are still far from normal. It should be remembered, too, that nephritis may reveal itself in the eve by the typical appearance of choked disk without any of the ordinary retinitis albuminurica. It is probable also that nephritis may cause serious damage to the optic nerve trunk through retro bulbar hemorrhages or localized areas of edema.

Since intranasal cauterization occasionally causes meningitis, it can easily be understood how it might also cause an optic neuritis, although in the case of Alt, in which one sided papillitis developed immediately after cauterization of one of the turbinated bones on the same side, there were no decided symptoms of meningitis, and a nearly complete recovery followed rapidly on the subsidence of the intranasal irritation.

While acromegaly generally causes atrophy by pressure of the enlarged pituitary body on the chiasma, it not infrequently produces optic neuritis.

cases of double optic neuritis which develop immediately after sunstroke or some violent physical exertion are probably due to hemorrhage or effusion within the cranial cavity, with secondary meningitis. In the only case following sunstroke which the writer has seen dementia and permanent blindness resulted. In a case following a violent run to catch a car useful sight was recovered after complete blindness bad persisted for months.

teeth or the reaction following their extraction may cause optic neuritis, apparently through the extension of phlebitis directly to the orbit or through the intervention of an abscess of the antrum of Highmore with secondary orbital cellulitis.

After taking account of all the known causes, there remain quite a number of cases of optic neuritis for which no probable cause can be ascertained. These cases, in the experience of the writer, are frequently monocular and may be slight or severe, but they offer, on the whole, a relatively good prognosis.

Diagnosis. The diagnosis of intraocular optic neuritis rarely offers any difficulty where the media are clear; the only conditions which are liable to be mistaken for neuritis are hyaline bodies in the papilla (to be discussed later) and an obscuration of the borders of the disk by opaque nerve fibers. Where these opaque fibers occur in solid patches they can hardly be mistaken for anything else, but where they occur sparingly mixed in with the ordinary sheath less fibers, the margin of the disk may be more or less completely obscured by a grayish striation, reminding one strongly of the appearance in a mild case of choked disk.' A careful examination of the direct image, showing the absence of enlarged capillaries, and other signs of stasis, will almost invariably clear tip the diagnosis, but where there is some functional disturbance this condition may occasionally cause some uneasiness, as is shown by a case seen bv the writer in which an ophthalmologist of the utmost ability diagnosed 'neuritis; subsequent continued observation showed that the cause of the blurring of part of the disk margin was due to this admixture of opaque fibers. If the media are not perfectly clear, it is not always possible to determine whether the cause of the blurred image of the disk is due entirely to the interference with the passage of the light. If the opacities in the media are easily detected, the observer will naturally be on his guard, but where the want of transparency is due to the extremely fine opacities which sometimes exist in the vitreous or upon the posterior surface of the lens, the beginner might easily overlook these, and, thinking the media clear, diagnose an incipient neuritis with blurred disk margins. To avoid this error one should, of course, examine the cornea, lens, and anterior vitreous with a strong convex lens.

Prognosis. This must always be guarded. There is absolutely Do means of determining whether a case of neuritis, seen for the first time, will result in total blindness or in the restoration of normal vision. Where the ocular disturbance depends upon some general affection the prognosis will depend upon the course taken by the latter: aside from the nature of the ultimate cause, the rule, as would naturally be expected, is that the greater the severity of the neuritis the greater the permanent damage to the sight, through the destruction of nerve fibers, during the neuritis or in the course of the subsequent atrophy. In general, it may be said that where the ultimate cause of the disease is not of a hopeless character the prognosis is relatively good, since useful central vision is often left, though frequently with more or less contracted fields. The writer has certainly seen and committed more errors on the unfavorable than on the favorable side of the question. Where the course of the neuritis has been rapid the vision is apt to improve with the subsidence of the ophthalmoscopic symptoms, sometimes becoming worse again when the secondary atrophy sets in. On the other hand, where the neuritis has run a long chronic course, with only a moderate amblyopia, the vision sometimes fails rapidly and continues to fail throughout the retrogressive stage. In still a third class of cases the writer has seen useful vision restored at the retrogression of a marked papillitis which had persisted with absolute blindness for several months.

Treatment. If the disease depend upon some general affection, the latter, of course, should first engage the attention of the physician, and the ocular condition may need no special treatment. Occasionally, however, it does, on account of the danger that while waiting for remedies to act upon the general condition permanent damage might be done to the sight, which could perhaps' be prevented by a mom vigorous line of treatment. Where the optic nerve lesion is not secondary to any other affection which requires attention, it is very uncertain what line of treatment will have most influence upon it. Full doses of salicylate of sodium or of iodid of potassium, mercurial inunctions (even in non specific cases), and the various forms of sweat cures have all been used with apparently good results in some cases, while in others they have had no influence. In very critical cases the writer has used the iodid of potassium, inunctions, and pilocarpin at the same time, with apparently good result. ,. Those who use mercury in non specific cases generally recommend it, in particular, where there is evidence of active inflammation, while others use large doses of iodid in precisely similar cases. A sweat cure, either with pilocarpin, salicylate of sodium, or the Turkish bath, is always in order. Where neither pilocarpin nor the salicylate, nor a combination of the two, can be borne in a sufficiently large dose to produce free diaphoresis once a day, and circumstances do not permit visits to a Turkish bath house, the Writer has found an improvised hot air bath, obtained by the use of a small lamp and enough rubber sheeting to cover two chairs, to be of great service, particularly in cases of nephritic origin. If mercury is used at the start in preference to the iodid, it may be exchanged for the latter when signs of mercurialization appear; and is use, in any case, should be continued off and on for months unless a complete cure should result sooner. Cupping or leeching the temples is still recommended by many and can do no harm. It is more than doubtful whether the use of setons in the temple or at the nape of the neck is even justifiable. In syphilitic lesions of the optic nerve, rapidly produced mercurialization by inunctions, repeated at intervals, with iodid in full doses during the intervals, gives the best results.

In the way of direct operative interference de Weaker's plan of incising the dural sheath may be mentioned as a curiosity.' From the standpoint of v. Graefe the proposal was a rational one, but the difficulties and dangers attending the operation have prevented its general adoption. More promising is the performance of trephining the skull, with or without the puncture of a lateral ventricle, where the neuritis is due to hydrocephalus internus, whether the latter be caused by brain tumor or by something else. Several cases of this kind are on record in which the operation has been followed by a marked improvement of the neuritis and of the vision. This treatment is of course resorted to only where the intracranial disease itself is of a very serious nature; and the relief and any improvement of vision obtained are not likely to be permanent, since the primary disease is generally incurable.

Where the neuritis depends upon the pressure of a brain tumor which can be removed completely, it may be permanently cured. Operative treatment may also cure a neuritis caused by an orbital tumor or by an inflammation or tumor of one of the accessory sinuses, or by any of the intracranial inflammations of otitic origin.

Acute or Fulminant Retro bulbar Neuritis. In the cases which v. Graefe originally classified here, blindness came OD suddenly, the ophthalmoscope showing very small but still permeable retinal arteries and a very slight blurring of the edges of the disk. He considered that the symptoms were due to a compression of the central vessels by the products of a retro bulbar neuritis. Some of his cases would now probably be called simply thrombosis of the central artery.

Etiology. In quite a number of cases severe exposure or rheumatism can be adduced as a cause of this affection; it has also followed infectious diseases, of which influenza seems particularly liable to produce it. In many cases no sufficient cause can be discovered. The disease seems to be one of the forms of multiple neuritis which may be produced by any of the toxins circulating in the blood. Acute or subacute myelitis is frequently accompanied by this same set of eye symptoms, excepting that the ophthalmoscope shows :a marked neuritis or a choked disk ; hence it is manifestly arbitrary to make :a separate group of the cases in which the neuritis happens not to reach as far toward the distal end of the nerve as it does in others.

Symptoms. At the present day the diagnosis of acute retro bulbar neuritis is made when one meets the following complex of symptoms: Pain back of the eye, spontaneous or upon movement of or pressure on the eyeball ; obscuration of vision, progressing in the course of from one to eight days to complete or nearly complete blindness ; Ophthalmoscopically, a normal disk or a hyperemia nerve bead with or without slight haziness of the surrounding retina; and, rarely, minute retinal hemorrhages and small grayish or yellowish spots in the neighborhood of the macula. With these symptoms are not unfrequently associated others pointing to acute myelitis or, more rarely, multiple neuritis. Death may occur within a few weeks of the onset of the disease.

Before amaurosis becomes absolute the sight may undergo sudden variations; thereafter it gradually improves slowly until, occasionally, normal vision is restored. Afore frequently the restoration stops short of this, and a certain degree of amblyopia remains either with a contracted field or with central scotoma, or with both. The color sense is apt to be severely affected throughout the disease. As the process begins to decline more or less complete atrophy of the disk occurs.

The affection may be one sided, or both nerves may be affected simultaneously, or there may be a very short interval between the attacks. In other cases recurring attacks at intervals of a month or more affect both nerves and one nerve after the other.

Pathology. What is known of the pathology of this affection we owe almost entirely to Achard and Guinon, Elschnig, Dreschfeld, and Katz, who have found interstitial neuritis generally throughout the whole diameter of the nerve, in some cases from the chiasma to the globe, with secondary degeneration of the nerve fibers. Whether similar symptoms may not be produced by a perineuritis or by a periostitis in the optic canal remains to be seen. As Elschnig suggests, the latter condition might cause a compression of the ophthalmic artery, and thus produce the ophthalmoscopic picture seen by v. Graefe. It is probable that still other cases are caused by a pachymeningitis spreading into the optic canals. Thus, in a case observed by the writer the patient had several attacks of complete double sided blindness at intervals of several months ; the attacks were preceded for some time by severe headache, and after the last attack an almost constant headache persisted for nearly a year.

Prognosis. The prognosis is favorable so far as the regaining of useful sight is concerned, complete blindness remaining very rarely, if ever. Serious permanent visual disturbances, however, are not unusual, and are apt to be worse in those cases in which the ophthalmoscopic symptoms of neuritis have been most pronounced.

Treatment. The same treatment as that recommended for optic neuritis in general should be ordered, especial stress being laid upon large doses of salicylate, of sodium where the affection seems to be of rheumatic origin.

Chronic Retro bulbar Neuritis. Perhaps some of the cases mentioned in the preceding section, where a succession of acute attacks occur, might properly be considered chronic. Besides these there are others which pursue a slower course, the loss of vision progressing during several weeks or months in the form of a central scotoma, at first relative (i. e. some or all colors being mistaken within its borders). Some cases are complicated by a peripheral contraction of the field, which in rare, severe instances may meet the central scotoma so as, to produce absolute blindness. The ophthalmoscope in the early stages may show nothing abnormal, or there may be congestion of the disk and slight haziness of the surrounding retina. Later, if the disease continues long, atrophy of the outer quadrant or half of the optic disk becomes evident, and occasionally the whole disk appears atrophic, even where the defect of vision is limited to a central scotoma.

Etiology. Some of these cases can be attributed to rheumatism or exposure ; in others chronic meningitis or periostitis in the optic canal may be assumed ; and sometimes no probable cause can be assigned. But the great majority are caused by systemic poisoning with alcohol, tobacco, lead, or some other drug or substance taken into or developed within the body, and they have been so long classified as toxic amblyopias that they and their pathology will be considered fully in another article (see page 459).

special form of retro bulbar neuritis, commonly known as hereditary nerve atrophy, is one which appears in members of the same family, generally between the ages of eighteen and twenty two, though it may occur as early as five years or as late as forty three. In the great majority of cases males alone are attacked, and, where the disease can be traced through several generations, it is generally transmitted by the unaffected females to their male offspring.

The course and ophthalmoscopic symptoms of the affection are those of a subacute retro bulbar neuritis, a permanent simple scotoma with more or less amblyopia almost always remaining, total blindness persisting very rarely. The cause of the affection has only been surmised!

Prognosis. In the cases caused by systemic poisoning the prognosis for the restoration of normal vision is good if the poisoning can be stopped before actual destruction of nerve tissue has taken place, and even where the ophthalmoscopic appearance and the duration of the affection would render complete recovery improbable, normal vision is restored in some cases.

In the non toxic cases the prognosis is not so good, owing to the doubt which generally exists as to the cause, and as to the possibility of any line of treatment really having much influence upon the course of the disease. Permanent blindness rarely results, however, and the more rapid the course of the affection and the less pronounced the ophthalmoscopic symptoms, the better the result to be expected.

Treatment. In the toxic cases the poisoning should be stopped, while in the others the same treatment recommended for the acute cases is in order.

Atrophy of the Optic Nerve. By atrophy of the optic nerve is meant, strictly speaking, the disappearance of a larger or smaller proportion of the nerve fibers, but practically the term is also used for any condition in which the ophthalmoscope shows the papilla or a considerable part of it to have permanently lost its normal tinge of pink, through the disappearance of a large proportion of the normal number of capillary blood vessels or through the formation of new connective tissue within it.

If the reduction of blood supply be only temporary, we may speak of anemia of the disk, or, if it occurs suddenly and is very extreme, of ischemia of the disk.

Varieties and Objective Symptoms of Optic nerve Atrophy. If the atrophy develop without previous inflammation of the nerve; it is called simple or primary or non inflammatory atrophy.'

The distinctions made by many writers between white and gray atrophy and between cerebral and spinal Atrophy are not well grounded, for the first refers merely to an appearance of the nerve which may be transient, a white atrophy sometimes passing over into a gray, and either being sometimes produced by the same cause; while the second depends upon the assumption that the optic nerve atrophy in a large class of patients is the consequence of spinal disease, whereas it is now known that the optic atrophy, while dependent upon the same cause as the spinal disease, originates quite independently of it and often antedates it.

In simple atrophy the nerve is white, bluish white, or grayish white, with clear cut edges, and frequently with a shallow excavation which may extend to the temporal margin, but which is generally not sharply defined. The vessels often show some reduction in size, but this is seldom extreme, as it is in some other forms of atrophy. In some cases the lamina cribrosa shows plainly, in others it does not (Plate 6, Fig. 111.).

The atrophy occurring after inflammation of the intraocular end of the nerve (neuritic or post neuritic atrophy) differs from the preceding form by more or less marked narrowing of the arteries, by the presence of white streaks of connective tissue along the large blood vessels, by more or less irregularity or obscuration of the margin of the disk, and by a chalky, opaque whiteness in contradistinction to the clear somewhat translucent appearance which is seen in most cases of simple atrophy (Plate 6, Fig. 11.). With the lapse of time, however, these differences are apt to become much less pronounced, and sometimes they disappear altogether. In some cases of neuritic atrophy a network of newly formed blood vessels is left upon the disk; and this symptom, when it occurs, is, in the writer's experience, the most permanent of all the signs of a previous neuritis. A moment's consideration will show that some cases of atrophy secondary to a neuritis will be classed, from the ophthalmoscopic appearances, with simple atrophy namely, those due to a pure retro bulbar neuritis, so that in speaking of a primary or secondary atrophy this exception should be borne in mind.

A third type of optic nerve atrophy is that described by Leber as retinal atrophy. This results from any extensive disturbance with the nutrition of the retina, and depends generally upon retinitis pigmentosa or extensive retino choroiditis. In this class of cases we find the most extreme changes in the blood vessels. In advanced cases of retinitis pigmentosa the vessels are very small, and sometimes are so reduced as to be indiscernible with the ophthalmoscope. The disk has a dirty bluish or yellowish gray hue.

In the various forms of retino choroiditis the changes in the vessels and the appearance of the disk are not apt to be so extreme; but where there is a large area of destruction, particularly at the macula, a corresponding sector of the nerve is generally atrophic.

The atrophy which follows embolus or thrombosis (embolic atrophy) of the central artery is also largely retinal in its origin i. e. it depends not so much upon the interference with its own blood supply (for this is in good part derived not from the central vessels, but from those of the sclerochoroidal ring) as upon a degeneration following the death of the nerve elements in the retina. It gives the nerve a dense, opaque whiteness or a yellowish white tint (Plate 6, Fig. IV.).

Subjective Symptoms. Except in the cases following retro bulbar neuritis of the macular bundle of fibers the disturbance of vision most commonly takes the form of a reduction of central acuity with contraction of the field at the periphery, but central and ring shaped scotoma, sector shaped defects, or spurious hemianopsia, all may occur (for visual fields see page 477). The color sense is apt to stiffer early in the course of the disease, the outer limits of the color fields sometimes being irregular or contracted before the field for white shows any abnormality. A diminution of the light sense is also common, the periphery of the field often showing a contraction, if it be tested with gray paper or by reduced light, when the ordinary test with a white object shows no abnormality (see page 168). On the other hand, some patients, especially in the atrophy accompanying retro bulbar neuritis' see better in proportion by a moderately dim light. In the occasional cases where the functions are normal and the disk decidedly atrophic looking, we have to assume either some congenital peculiarity or that the connective tissue has been changed chiefly in appearance, without sufficient increase in volume to cause atrophy of the nerve fibers.

Etiology. It is evident that any of the causes which have been enumerated as producing optic neuritis may produce atrophy, and, as the signs of neuritis may have disappeared by the time the patient is first examined, the results of the cause may be set down as atrophy without any knowledge of the neuritis. Besides neuritis, any other cause that cuts off communication between the retina and the higher nerve centers will produce atrophy.

Brain tumors may cause atrophy, by the production of neuritis, by direct pressure on the nerve, chiasma, or tracts, by the pressure upon the chiasma and tracts of the accumulation of fluid in the ventricles which often accompanies them, or by raising tip the chiasma and nerve, and thus causing them to be constricted by the arteries at the base of the brain.

Injuries to the nerve trunk are followed by atrophy, both ascending and descending, while all the various processes which destroy the function of the retina, whether it be removal of the globe, the various conditions which produce phthisis bulbi, inflammations of the choroid or retina, detachment of the latter, or cutting off its blood supply through thrombosis or embolism, and, finally, abnormal pressure both upon the retina and the disk, as in glaucoma, produce ascending atrophy of the nerve trunk, chiasma, and the tracts leading to the higher cerebral centers.

The atrophy which sometimes follows erysipelas of the face is undoubtedly caused by the accompanying inflammation in the orbit, since any severe orbital cellulitis May cause atrophy, probably either by direct pressure on the nervetrunk, by thrombosis of the retinal vein, as pointed out in particular by Knapp, or by producing a neuritis. Some authors doubt whether atrophy may result simply from hemorrhage into the orbit, but the writer has seen at least two cases in which this undoubtedly occurred: in one a hemorrhage followed an extirpation of the lachrymal gland and led to atrophy, with the typical picture of thrombosis of the retina] vein and paralysis of all the ocular muscles; this indicating that even if the vein had not become obstructed, atrophy might have resulted directly from the pressure.

In a number of cases optic nerve atrophy follows falls or blows upon the head, without any signs of meningitis or optic neuritis. The first rational explanation of these cases was given by Holder and Berlin, who found that in many cases, without any external signs of fracture, fissures of the walls of the orbit were produced which extended into the optic canal, the nerve in some cases apparently being injured immediately by pressure from fragments of the bone or by hemorrhages into the optic canal, or later by pressure from the development of callus. In the first two instances blindness develops at once; in the last it comes on gradually after several days or weeks. These cases are generally one sided, and apparently may be produced through contre coup by v0ence to distant parts of the body. Whether the cases described by Schweigger as concussion of the optic nerve were due to fractures of the bone is uncertain. In them violence to the bead was followed by immediate and complete one sided amaurosis. A certain amount of useful vision (in one case nearly approaching the normal, the nerve showing partial atrophy) returned after some days or weeks. It is possible, also, that some of the atrophies which follow spinal injuries are produced in this way: about the real significance Of these cases there has been some dispute, some authors leaning to the view that they were the result of a trophic disturbance, while others assume that they result from an ascending meningitis; but since it has been shown that a fall u on the trochanter, for instance can produce a frac¬ture through the optic canal by contre coup, it seems probable that at least some of the cases have this origin.

The numerous cases of optic nerve atrophy in various forms of spinal disease also led to the belief, at one time prevalent, of a trophic connection between the spinal column and the optic nerve; and because the disk in many of these cases (though by no means in all) was of a grayish line, it was common to speak of gray or spinal atrophy. The spinal affection in which atrophy is most commonly observed is tabes. Out of 109 cases of tabes which Berger examined be found optic nerve atrophy in 44, and amblyopia, with normal disks in 7. It may be one of the earliest symptoms of the disease, occurring entirely independently of the spinal lesion, and beginning, apparently, near the peripheral end of the nerve. In the early stages the ophthalmoscope sometimes shows a decided congestion of the disk, though the ophthalmologist seldom sees the patient early enough to observe anything but atrophy, which may be either of the gray or white variety. The disturbance of vision generally takes the form of a peripheric contraction of the field with reduced central acuity, but central scotoma sometimes occurs. The affection almost always ends in complete blindness if the patient live long enough.

In disseminated sclerosis the frequently occurring atrophy, which is often confined to the other half of the disk and produces a relative central scotoma oftener than a contraction of the field, is sometimes preceded by moderate papillitis, and is much less likely to lead to blindness than the atrophy of tabes. The disturbance of vision is more subject to variations, and is not infrequently accompanied by nystagmus, which becomes more marked or shows itself only on voluntary movements of the eye.

In progressive paralysis, also, optic atrophy is quite common, and that it may be a very early or perhaps an initial symptom is indicated by the fact that a large proportion of patients in whom apparently idiopathic optic atrophy occurs sooner or later become demented. Here, too, Allbutt has observed a stage of congestion preceding the atrophy.

According to Michel, the atrophy occurring in multiple foci of cerebral softening as a rule affects only the temporal side of the disk. Atrophy has also been observed in chronic bulbar paralysis, in chorea, in epilepsy, where it is probably only a coincidence, and in nearly all of the general affections which have been mentioned in connection with neuritis.

Atrophy is quite common in diabetes mellitus; it also has been noted with diabetes insipidus. One important cause of atrophy is pressure upon the nerve or chiama at the base of the brain or within the optic canal by enlarged arteries. The enlargement may be aneurysmal, but commonly it is merely the result of arterial sclerosis, and the resulting pressure on the nerve may spread the latter out in the form of a semi cylinder or even divide it into two bundles.

The atrophy which follows severe hemorrhages is sometimes preceded by neuritis. The blindness is often complete and generally double sided. It comes on sometimes at once, but, as a rule, several days after the hemorrhage, and, according to Fries, out of 90 cases the highest degree of amaurosis attained in the course of the case underwent no improvement in 43; in 28 partial recovery took place, while full vision was restored in 19 cases. The sources of the hemorrhages are most frequently the alimentary canal (stomach and intestines), the uterus, veins (venesection), the nose, accidental wounds, the lungs, and the urethra, in the order named. Women are attacked with only slightly greater frequency than men. The immediate cause of blindness is probably, in the cases occurring at once, ischemia of the nerve and retina; in the others hemorrhages into the nerves, nerve centers, or intervaginal space from malnutrition of the vessel walls. In one case a microscopic examination showed fatty degeneration of the nerve fibers and retina.

Incurable atrophy has occurred in some cases of lightning stroke, while in one reported case the pallor of the optic disks, the small retinal vessels, and the great reduction of sight improved to normal or nearly so on the use of nitro glycerin. The atrophy from a affections of the accessory sinuses will be discussed later on.

Under the bead of congenital atrophy are grouped a number of cases, probably of various origins, which have been observed in infants. Some of these are doubtless the result of neuritis or of hydrocephalus in utero or soon after birth ; in others, judging from the entire absence of retinal vessels, there is a fault of development; while still others, which have been observed especially after forceps delivery, are probably the result of injury to the bones of the head.

Hydrocephalus internus, although, as has been mentioned, it sometimes produces neuritis, is generally found to have produced atrophy, probably by direct pressure upon the chiasma. and tracts.

In quite a large proportion of cases Leber estimates it as high as 50 per cent. the most careful examination fails to reveal any cause for the atrophy. In these cases and in those occurring in the course of spinal diseases men far outnumber the women, and old persons the young. In all forms of atrophy, except where caused by affections of the orbit, globe, or accessory sinuses, double sidedness is the rule.

Pathology. In the atrophy following neuritis, largely as the result of pressure both from the edema and the new connective tissue, the nerve fibers degenerate, their sheaths (in the medullated portions) being first transformed into fatty looking globules and granules, leaving only the nerve fibrils, which themselves become varicose, and then shrink into very fine homogeneous fibrille or disappear altogether. The new connective tissue may fill up the papilla entirely, and the larger vessels running through it generally have much thickened walls.

In the simple or gray atrophy ("gray atrophy," in a pathological sense, refers strictly to the macroscopic appearance of the cut surface of the nerve) a similar process of degeneration takes place without any ascertainable preceding inflammation. It may occur in isolated foci or may affect the greater part of the nerve at once. in old, extreme cases, either of simple, neuritic, or direct pressure (from tumors, etc.) atrophy, all signs of nerve substance may disappear entirely, and only a cord of connective tissue remain.
In a certain sense “normal “optic atrophy has been reported by Fuchs in the form of degeneration of a number of the most peripheric bundles of fibers in a large proportion of healthy adults. This observation is disputed by Michel.

Diagnosis. The variations in the normal color of the disk are such that it is sometimes impossible to say whether an observed pallor is abnormal or not. Here the subjective tests are of great importance, the examination of the field for white and for colors being made with the utmost care both by full and by reduced light. To illustrate the importance of this a case may be mentioned in which, with decided atrophy of one quarter of the disk of one eve, with an absence of one quadrant of the field for white and of the nasal half of the field for colors, no trouble was suspected with the other eye, it being apparently normal both subjectively and objectively. But, while the vision was practically normal and its field showed no defect for white, an examination of the color limits showed that in the nasal half of the field both quadrants had lost the perception of green and one quadrant that of red, thus indicating with the greatest probability the implication of both nerves or of the chiasma.

In other cases, as mentioned above, an eye showing no defect in the field by good light will, when tested in a moderately dim light or by using a gray paper as a test object, show marked abnormalities. In many cases, where there is no question about the existence of atrophy, a careful consideration of the symptoms is of importance in the attempt to determine the location of the primary lesion or to decide on the nature of the general disease of which it is but one of the manifestations. Where the trouble is entirely one-sided the lesion must, in the great majority of cases, be peripheral to the chiasma, but not necessarily, for an intracranial lesion might affect one side of one optic tract so as to produce a one sided disturbance of sight, either crossed or on the same side. In nearly all cases, however, any affection of the chiasma or tracts will produce a double sided disturbance in the fields, generally more or less symmetrical, pressure on the chiasma in front or behind tending to produce defects in the temporal halves of the fields; while symmetrical defects in the nasal halves indicate pressure on or lesion of tile outer side of the chiasma, tracts, or intracranial portions of the nerves (see pages 480 an ( 481).

An enlargement of the blind spot may indicate the existence of the so called normal atrophy of Fuchs (granting that this actually occurs), or a mild peripheral perinuritis, or some other affection attacking only the fibers close to the periphery toward the distal extremity of the nerve. A central scotoma, either relative or absolute, indicates, of course, an affection of the papillo macular bundle of fibers, but, unless there have been symptoms of congestion of the disk to indicate an implication of the distal extremity of the nerve, we have Do way of judging whether the lesion is nearer the globe or the brain unless there occur with it an enlargement of the blind spot; in which case, as Berger has recently pointed out, we may with Some certainty diagnose distal perineuritis, either present or past. In deciding between atrophy from tabes and from disseminate sclerosis it should be remembered that disorders of the pupil reaction are much more common in tabes, while nystagmus of recent origin and paresis of other than ocular muscles strongly indicate disseminate sclerosis. The partial atrophy occurring in cerebral softening has already been referred to. In all cases of atrophy, as of neuritis, the importance of as thorough an examination as is practicable of the general system, reflexes, urine, etc. should Dot be forgotten.

Prognosis. The prognosis of post neuritic atrophy is, like that of the neuritis itself, relatively favorable, since the sight that is left after the neuritis has run its course is apt to be retained. In some cases normal vision is kept, but, as a rule, there is a reduction of central acuity with contraction of the field, except in cases in which the lesion has mainly affected the papillo macular bundle, where a central scotoma with normal peripheric field limits is the rule.

In the cases of simple atrophy the prognosis will depend upon the cause if this can be ascertained. In tabes it is almost unqualifiedly bad: once having set in, the loss of sight generally progresses until the patient is blind. In disseminate sclerosis blindness is rare, and in some cases the vision, after being much reduced, undergoes considerable improvement. In the other cases of simple atrophy the prognosis must always be dubious if there is evidence of recent progress. The majority of them sooner or later, in spite of all treatment, end in blindness. Yet the surgeon must be careful not to be too positive in his expressions of pessimism, for every now and then one sees a patient apparently doomed to blindness, one eye being already practically blind, with marked symptoms of progressive atrophy in the other, where to his surprise the process stops and useful sight is retained for years.

In toxic amblyopia, the papilla occasionally presents the appearance of a general atrophy, and where this occurs, with some slight Contraction of the field, with myotic pupils, and with peripheral paralysis due to alcoholic neuritis, the diagnosis of some grave incurable disease may be erroneously made in spite of the central scotoma, since such scotomata are not infrequent in some such diseases, and sometimes, though rarely, occur in tabes. On the other hand, a too favorable prognosis may easily be made with patients who have atrophy of the outer quadrant or half of the papilla, with a central scotoma, relative or absolute. In such a case, if the patient happen to use tobacco or alcohol freely, it would be natural to think of toxic amblyopia and give a relatively good prognosis, although the use of these stimulants may be a mere coincidence, and the trouble may continue to progress in spite of total abstinence, the atrophy being due to some entirely different cause. In two cases of this kind, which the writer has seen, the central scotoma was decidedly less marked, in proportion to the amount of atrophy and reduction of vision, than is usual in toxic amblyopia. The only safe plan, if there are no indications of disseminate sclerosis, cerebral softening, or other serious nervous disease, is to await the result of abstinence before making a diagnosis or prognosis.

In the rare cases of spurious hemianopsia, when, with progressive atrophy, the fields happen temporarily to closely resemble those in homonymous hemianopsia, the beginner might consider it to be a case of cortical hemianopsia and give much too good a prognosis as to the chance of progression. In such cases the history, the more pronounced atrophy of the disk, the undue reduction of the central vision, and the, disturbance of the light or color sense in the remaining halves of the fields, will almost certainly allow the proper distinction to be made.

Where from the previous existence of a large physiological excavation, or from an unusually high normal intraocular pressure, or from the nature of the initial lesion, a case of simple atrophy exhibits a deep, sharp bordered excavation, the problem of distinguishing it from simple glaucoma with no appreciable hardness of the globes may arise, and its solution may be very difficult or, in some cases, at first impossible. There are no points of difference upon which absolute reliance can be placed. The most valuable are the occurrence in glaucoma of an unusually good color sense in proportion to the contraction of the field, and the ease with which pulsation of the retinal arteries may be produced by light pressure on the globe. All the conditions have to be carefully weighed in such a case, and occasionally no positive diagnosis can be made at once. If, after continued observation, the doubt should persist, it is better to use a myotic, or even to operate, than to allow the patient to go blind by default. (Compare with page 382.)

Treatment. The results of the treatment of optic nerve atrophy are extremely unsatisfactory. It is entirely probable that, except where it depends upon some still active inflammatory process, upon some toxemia, or upon some neoplasm which can be removed, no form of treatment has any influence upon it. This does not mean, however, that nothing should be done for the patients. In the hope that there may still be some active process capable of being influenced, large doses of iodid of potassium may be tried, or mercury may be used if there is any suspicion of syphilis, though, as a nerve poison, it should be used with great care if there is any spinal trouble. It is common to use strychnin in many of these cases, and it is probably well to try it in full doses (increasing from 1/20 ¬grain three times a day, if given by the mouth, to the limit of toleration or injecting from 1/40 to 1/2 0 under the skin of the temple. It often causes a slight temporary improvement of central acuity or of the extent of the field, and a number of cases have been reported in which its effects have seemed almost miraculous. In conjunction with strychnin, nitroglycerin should be exhibited.

Electricity in the form of a mild constant current may be used for a few minutes every day or two, though little more can be said for it than that it gives the patient the benefit of the doubt. Nitrate of silver is another remedy in common use which is supposed by some observers to have a particular value in checking post neuritic atrophy, and cyanid and arsenite of gold, phosphate of zinc, and numerous other remedies have received enthusiastic recommendations. Where there are evidences of active inflammation at the base of the brain a vigorous course of salicylate of sodium, iodid of potassium, inunctions of mercury, or some form of sweat cure, or any two or three of these together, should never be omitted. The writer's plan is generally, as in the case of neuritis, to give the salicylate a trial of about a week (15 grains eight to twelve times a day in brandy); then, if no decided effect has been produced, to change to large doses of iodid in connection with the sweat cure (pilocarpin to grain in a glassful of hot whiskey and water, with the addition of 15 grains of meliorate of sodium if the pilocarpin alone does not produce free diaphoresis).

It is in these cases of meningitic atrophy that Valude has recommended antipyrin.

Tumors of the Optic Nerve. The primary tumors of the optic nerve trunk are most frequently of the sarcomatous type, with a tendency to myxomatous degeneration. Sarcoma, myxo sarcoma, myxoma, and myxo fibroma are the commonest types, in the order named, though. glioma, psammoma, endothelioma, and neuroma have also been described, the last named very rarely.

The point of departure seems to be the pial sheath and the septa of connective tissue running off from it into the interior of the nerve, the tumor sometimes developing uniformly throughout its diameter, but more frequently with a tendency at first to spread along the pial sheath in the form of a cylinder, through the center of which the more or less degenerated trunk of nerve fibers runs, though at the oldest portions its identity is often entirely lost. These tumors are generally somewhat spindle shaped, tapering at least at one end. They never invade the globe (unless a recent case of Risley is an exception), and when they grow forward close to it a sharp constriction separates them from it; when the tumor is continued into the cranial cavity there is a narrowing corresponding to the optic canal.

From a pathological standpoint, though not necessarily differing in the symptoms which they produce, are to be distinguished the growths which take their origin in the dural sheath. They are apt to be fibromata, endotheliomata, or sarcomata; they generally affect the nerve trunk only by direct pressure or by interfering with its blood supply.

As secondary tumors glioma and melanomatous sarcoma, spreading from the interior of the globe, are most common. Carcinoma has also been observed, in one case as metastasis from the kidney; in another, that of Krohn, already referred to as unique, a metastasis from a carcinomatous ovary occurred in each optic nerve immediately behind the globe. Gummata and sometimes very extensive tuberculosis of the optic nerve have also been reported. In the case of Sattler the tuberculosis of the nerve and its sheaths produced a tumor 18 mm. in diameter by 25 rum. in length. Michel has reported an unique case in which a patient, suffering from elephantiasis of the leg, but with good sight, was found after death to have the chiasma and the intracranial portion of one nerve very much thickened by the uniform distribution, between the bundles of fibers, of numerous flbrils similar to those of elastic tissue.

Symptoms. Tumors of the nerve are apt to occur in children, and there is a certain amount of evidence to indicate that contusions of the eye and its vicinity play a part in their etiology, though sometimes their beginnings are probably congenital. Their growth is slow, and pain occurs, if at all, only after they have attained considerable size. If the patient is a child, usually the first symptom to attract attention is protrusion of the globe. This is at first, and sometimes throughout, straight forward, but as tile tumor gets larger its impingement upon the upper and inner walls of the orbit sometimes forces the eye slightly down and out. In this stage the general motility of the globe is sometimes impaired, while in the early stages it is remarkably well preserved.

If examined early, the eye may show signs, sometimes very pronounced, of optic neuritis; later on, of atrophy. The pupil may be wide through pressure paralysis of the oculo motor or from the loss of sight. In older patients the existence of the tumor is frequently first suspected from the loss of sight, which generally progresses rapidly, though to this there are occasional marked exceptions, as in the case of v. Graefe, where the chiasma and adjoining portions of the optic nerve were found converted into a gliornatous tumor in which it was difficult to make out any of the scattered nerve fibers although up to a short time before death the sight had been more than normal. In a more recent case of Wiegman, a well developed tumor of the trunk of the nerve, spreading the bundles of fibers widely apart, existed with a vision of 20/20 (in the other eye 20/15) and a normal field. In such cases the development must have taken place very gradually, so as to allow the nerve fibers to accustom themselves to the pressure and change of position.

Diagnosis. The main points in the diagnosis between these and other tumors of the orbit are the slow and relatively painless progress (though this may apparently be hastened by an injury), the propulsion straight forward or nearly so, the Iong retained motility of the eyeball, and, with the exceptions noted above, the early loss of sight.

Prognosis. Prognosis as to sight is of course unqualifiedly bad, that as to the chance of retaining the globe fair, while as to the prevention of recurrence after removal it is decidedly good unless there be involvement of the extra orbital part of the nerve. To help decide this point, an examination of the field of the other eye is very important, for if it shows a well marked defect, without other cause, an implication of the chiasma is probable; and, while this should not necessarily contraindicate an operation, the prognosis should be very carefully guarded.

Treatment. Removal is the only treatment allowable, and it is probable that this can, in the majority of cases, be done with retention of the eyeball, although hitherto the globe has in most cases been sacrificed also. In 8 cases, beginning with one of Knapp's, the nerve has been cut close to the eyeball and at the extreme apex of the orbit, and the intervening portion of the nerve with the tumor removed, the eye being left in place. In most cases, the internal or external rectus muscle was cut to aid in exposing the tumor, but in one case (Knapp's second one) the tumor could be brought into view through an incision between the internal and inferior rectus and removed without cutting any muscle. In 4 of these cases the eye retained its normal appearance, in 3 it became more or less phthisical, and in 1 there was sloughing of the cornea through exposure from extreme protrusion. The method to be recommended is that of Lagrange,' who enlarges the external commissure, cuts the external rectus, leaving attached to it a long thread, puts a thread through the tumor by which it is drawn forward as far as possible while the nerve is being cut at the external optic foramen. The nerve is then cut close to the globe, the tumor removed, and the external rectus and conjunctiva reunited. Since one of the subsequent dangers is sloughing of the cornea from exposure (in Knapp's ease this occurred in spite of repeated suturing of the lids), it is well to check the bleeding as quickly as possible by pressing back the ball firmly before stopping to suture the muscle; this is to be followed by a pressure bandage and prophylactic lid sutures.

Hyaline Bodies in the Optic Disk. These bodies (known also as colloid bodies, verrucosities, or " Drusen ") were first discovered in microscopical specimens examined by Muller and by Iwanoff, and for years little was known of the ophthalmoscopic picture which they presented.

Symptoms. When seen during life, if there are but few of them and they are rather deep seated, they can be barely distinguished as somewhat spherical bodies of a lighter hue than the rest of the disk. In this case they are best seen, as Liebreicb suggested, by throwing the brightest part of the light a little to one side of them. When nearer the surface they may be scattered through the disk or occur more commonly in groups at its periphery (Fig. 264). They are somewhat translucent, and in some cases give back quite a brilliant reflection. When they project well above the surface of the disk they often remind one of half soaked grains of tapioca. In other cases they are of a denser or slightly yellowish white. In the direct image they appear to be about 2 3 mm. in diameter, but occasionally bodies two to three times as large are seen. The entire border of the nerve is occasionally obliterated by them, and sometimes they encroach upon the disk so as to entirely conceal its normal tissue, in its place appearing a mulberry like mass, from the center or sides of which the blood vessels appear. A slight encroachment upon the retina is common, and occasionally isolated granules are seen well out from the main body. More rarely large masses of them develop out from the edges of the disk into the retina. Fig. 265 represents such an extreme case, in which some of the arteries appeared as white cords with a very minute column of blood in the center. In this case, repeated small hemorrhages took place from the retinal vessels.

The affection is a rare one, occurring in the writer's experience in 1 out of about 2000 cases. It is met most frequently in cases of retinitis pigmentosa, but, aside from this, the eyes in which it is seen with the ophthalmoscope are, in other respects, often entirely normal, though there is some rather unsatisfactory evidence tending to connect its origin with injuries to the eye, with neuro retinitis, and with Bright's disease.

Few cases have been observed long enough to note any change in the ophthalmoscopic appearance, but where this has been done a gradual increase in the number of the bodies has sometimes been noticed. It is generally stated to be a double sided affection of advanced life, but the writer has seen it quite as often in young adults as in older patients (in one case at nine years), and in one disk alone as often as in both disks.

Pathology. Our knowledge of the more intimate character of these bodies we owe chiefly to Hirschberg and Cirincione, Gurwitsch, de Schweinitz, and Sachsalber. They are found to be made up of a rather hard hyaline substance, the smaller bodies, on cross section, showing well marked concentric lines, the larger bodies being made up of a number of the smaller ones more or less blended to ether. At points they show a tendency to calcareous degeneration. Tincture of iodin gives the substance a yellowish color, and no amyloid reactions are obtained with saffranin and methyl violet. The earlier view was that these bodies had the same origin as the colloid excrescences of the lamina vitrea of the choroid, while the tendency at present is to regard them as something entirely different. It is certain that they have no necessary connection with the lamina vitrea ., for, while a favorite place for the development of the largest masses is just between the termination of this membrane and the central vessels of the nerve, they may also occur well out in the retina and in the nerve, posterior to the lamina cribrosa. Granting this, it has not been shown that their composition differs essentially from that of the “Drusen “of the choroid (consult Fig. 318, page 496).

Diagnosis. In the less pronounced cases, the affection is easily overlooked, for it is only by careful examination by the direct method that the rounded outlines of the bodies can be made out. In a more pronounced form, especially where they are grouped around the periphery of the disk, they may be and have been mistaken for optic neuritis, from which, however, a careful direct" examination will always enable them to be distinguished. The most pronounced cases look like nothing else to be seen at the disk, but they might easily puzzle the beginner, especially since, in many text books, they are not mentioned.

Prognosis. In the cases observed during life, the vision has usually been found to be normal (except in the cases accompanying retinitis pigmentosa, in some, even where they were so abundant as to nearly conceal the disk; and where moderate development of them is discovered by accident, as is generally the case, they need cause no alarm, but it remains to be seen whether in extreme and progressive cases they May not cause serious trouble. The case represented in Fig. 265 was one sided, and the eye was entirely blind, but it is not certain that the blindness may not have been due to some other cause.

Treatment. Treatment is not necessary in the great majority of cases, and it is not easy to understand how anything could be used that would affect them.

Hemorrhages in the Optic Nerve or in the Intervaginal Space After a hemorrhage at the base of the brain or in the optic canal, or even from a more peripheral source (after a contusion of the eye), the blood may flow into the intervaginal space and distend it widely at its distal extremity.

In such cases the sight may be suddenly lost, the ophthalmoscope showing a somewhat blurred disk, with the central vessels reduced in size, sometimes with a red spot at the macula surrounded by a grayish area, as in embolus of the central artery, and, later on, the dissolved hemoglobin may find its way into the disk, so as to be seen with the ophthalmoscope, leaving deposits of pigment there by which the nature of the original process may be recognized after months or Years. The nerve atrophies, and the vision does not return at all, or does so but imperfectly. Where there is no history of violence the affection might be mistaken for a rapidly developing neuritis or for embolus or thrombosis of the central artery which latter may indeed possibly be produced by it.

Much more rarely a hemorrhage occurs within the pial sheath, and may find its way along the septa of the nerve trunk. This has been observed in connection with Bright's disease.

Optic nerve Lesions from Affections of the Accessory Sinuses. Inflammation of any of the sinuses or of the ethmoid cells may cause optic neuritis and atrophy, by spreading to the orbital tissue or to the cranial cavity ; or by the direct pressure of their distended walls upon the orbital tissue, in the case of the ethmoid cells, and possibly of the maxillary and frontal sinuses.

Affections of the sphenoidal sinus have an especial significance for the ophthalmologist on account of the intimate relation between the walls of this cavity and the optic nerve. Fig. 266 shows part of a coronal section through the skull passing through the optic canals. A glance at the left side of it, with a realization of the fact that the thin bony partition separating the optic canal from the sinus is sometimes imperfectly developed, will show how easily an inflammation of the sinus might cause localized neuritis, with subsequent descending atrophy, through the diffusion of ptomains into the nerve, or an actual infection of the intervaginal space, leading to perineuritis and choked disk; or an atrophy through direct pressure, if the walls of the sinus were distended by fluid or by a tumor. These considerations should lead one to take the sphenoidal sinus into account in all cases of obscure optic nerve trouble, especially since at least one case has been reported (Holmes) in which a puncture of the anterior wall of the sinus drew off a collection of pus and cured an optic neuritis.

The right side of the section represented in Fig. 266 illustrates a point which seems to have attracted very little attention namely, that in some heads, on at least one side, the cavity in closest proximity to the optic canal is not the main sphenoidal sinus, but an entirely separate' cell, opening into the nose by an independent foramen which is sometimes so large that the cell could, with propriety, be described as the upper extremity of the nasal cavity. A collection of pus in this space might cause a disturbance of sight, with symptoms of suppuration of the sphenoidal sinus, although an operation on the latter would give no relief. To operate on this anterior sphenoidal cell or prolongation of the nasal cavity would be more difficult and dangerous than to puncture the main sphenoidal sinus, but knowledge of its occasional relation to the optic canal may serve to explain some cases of optic nerve trouble in which an ordinary sphenoidal operation gives negative results.

Congenital Anomalies of the Optic Nerve. Aside from congenital atrophy of the optic nerve due to intra uterine neuritis, hydrocephalus, and other causes, the nerve in the various degrees of microphthatmos and anophthalmos shows more or less marked signs of imperfect development. It may be entirely absent, or represented only by a cord of connective tissue, or it may simply have an abnormally small proportion of nerve fibers. Even more interesting is the case cited by Manz, which, though old, is apparently quite authentic, of entire absence of any decussation of the optic nerves, the latter running direct to the respective sides of the brain, without any sign of a chiasma

Some of the anomalies of the nerve which have been discovered with the ophthalmoscope are discussed in the section on the Ophthalmoscopic Examination of the Fundus (pages 191 195). Of these, the condition known as coloboma of the optic nerve or coloboma of the optic nerve sheath is the most important. In the most common type, one sees in place. of the disk an excavation several times as large as the ordinary papilla, generally much deeper and with a sharply excavated border below, while, above, its floor comes gradually up to the level of the surrounding retina; the main vessels curve abruptly over the lower edge, while the bottom of the excavation may be entirely free from them or may have some running across it to the upper part of the retina, crossing the upper border without any break in their continuity at that point. The excavation is surrounded by a generally complete pigment ring, outside of which there is often a narrow white zone or crescent. If there is any sign of normal disk tissue, it is apt to he above. More rarely, the entire floor of the excavation is deep below the retina, with vessels curving sharply around its border at various points, though chiefly below and above (consult Fig. 141,).

The few microscopical examinations which have been made of the common form of this anomaly show that it depends upon the non closure of the fetal optic nerve fissure; the central vessels enter the nerve proper only in part, or more commonly not at, all, but enter the eye through the mass of connective tissue which takes the place of the dural sheath below. In one case (Magnus) the fissure seems to have been at the nasal side instead of below the nerve. The deep atypical excavations which are sometimes seen within the borders of otherwise normal papilla are probably due to a less marked failure of development of the same nature.

Another type of anomaly, which has also been described as coloboma of the nerve, consists in the absence of a zone of choroid (often wider below) around the otherwise moderately normal papilla, the blood vessels appearing near the center of the latter and passing across the borders of the zone without any displacement or other sign to indicate any considerable excavation. These cases, in the opinion of the writer, would be more accurately designated circumpapillary coloboma of the choroid, and to this class the cases exhibiting mere crescents of choroidal absence below the papilla are most probably allied.

Coloboma of the nerve is generally associated with imperfect sight and often with nystagmus or microphthalmos. It may affect one or both eyes, and its etiological relationship to coloboma of the choroid is shown by its occurring sometimes in the same eve with the latter, or in one eye of an individual having coloboma of the choroid and iris in the other eye.

The bands of connective tissue not infrequently seen upon the disk may be, as Masselon suggests, prolongations of the lamina cribrosa, though they sometimes, as in Fig. 267, appear to have no connection with it. In extreme cases, as shown approximately in Fig. 268, the entire disk may be concealed by a pearly, bluish white mass of connective tissue.

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