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Chapter VII Amblyopia And Amaurosis

The terms "amblyopia" and "amaurosis," in their original acceptation, designate only a symptom viz., a diminution or loss of the visual function. They are now, however, employed with a more restricted meaning, and are used to describe cases of visual weakness, in which, after thorough examination by all the methods at command, we can neither find any lesion whatsoever, nor any atrophy of the optic nerves.

The diminution may then be considered as due to an interruption of power of transmission in the nerve (von Graefe). It is, therefore, of importance, in diagnosing amblyopic affections, to exclude with certainty any disturbance of the transparency of the media, diseases of the membranes which form the eyeball, and all anomalies of refraction and accommodation.

This being done, it remains for us to examine, according to the method already indicated (see P 37), the visual acuteness at the centre (V) and at the periphery (Ve). This examination should also be conducted in a darkened room, with a lamp, the int ensity of which can be approximately regulated, so that we may judge of the effect of various degrees of illumination on the visual field.

Moreover, a thorough examination of the visual field can only be made with a perimeter (P. 39) and by taking into account the percept tion of colors. Von Graefe classifies the various conditions of vision, revealed by functional examination, under three leading categories:

  1. Central vision is to a certain extent impaired, whilst the peripheral vision is absolutely normal. This condition, especially when the disease has already lasted for some time, almost certainly excludes the idea of progressive amaurosis.
  2. The central vision being impaired, the peripheral is also diminished to a like extent; as a rule, there is a concentric contraction proportional to the decrease of central acuteness (the visual field is relatively normal). There, the functional disturbance does not suffice of itself to indicate the gravity of the disease. The condition of the optic papilla, and the duration and mode of development of the disease, must also be taken into account. This form specialty lends itself to rational treatment stilled to die condition of the individual.
  3. 'PlC diminution of the peripheral vision is irregular and defective (scotoma), and does not correspond to the central vision (the visual field is abnormal). In this variety, the prognosis is less favorable. Yet, although recovery is scarcely ever possible in such cases, the condition may sometimes remain stationary, as for example in hemianopsia. (See article on Hemianopsia.) As a rule, when the amaurosis is dangerous, the vision of one eye is very seriously compromised before the visual acuteness of the other begins to diminish. We must then study the development in the second eye, so as to ascertain if the disease follows the same course in it as in the first. In this way we often obtain information as to the future of the disease. The anomaly of the visual field most frequently begins to appear on its external side; but it is by no means rare to find it first on the inner side.
Apart from these functional symptoms, a certain importance is also to be attached to other phenomena, such as photopsia, chromopsia, musce volitantes, etc. Yet these phenomena belong rather to diseases, of the internal membranes of the eye, and are not peculiar to amaurotic affections (consult the articles on Hyperesthesia and Anesthesia).

As to the difficulty in distinguishing colors (pathological dyschromatopsia), we have already said that this defect begins with the green,. and extends to the red, to the yellow, and finally to the blue; we have also proved that the progressive loss of the power of distinguishing colors is not in accordance with the diminution of the visual acuteness. Yet, there is often a certain relation between these two functions, in so far as a diminution in the intensity and extent of color perception precedes, both at the centre and periphery of the visual field, any diminution of the visual acuteness at the same place. This symptom thus acquires a certain importance in the prognosis. When we find. central amblyopia with absolutely normal peripheral vision, and, at the same time, a diminution in the color perception, the prognosis is less favorable than when the chrornatic sense remains intact. We must not however, at once conclude that we are dealing with progressive amurosis, even when there is a slight discoloration of the optic papilla, for observation has shown that the disease may be permanently arrested. When the defects of the visual field (scotomata) are stirrounded by a zone which preserves its color perception, we may admit that the scotoma will not extend for the present, but we must be guarded in giving our prognosis, for it may ultimately make progress.. If there is already chromatic insensibility in the neighborhood of the scotoma, we may be sure that the mblyopia will also extend to these parts.

The examination of the phosphenes gives less certain results than the objective examination of the visual functions. It is only of value in a very limited number of cases, in which the phosphenes still remain in portions of the retina insensible to light. Next in order to the functional examination, the condition of the optic papilla decides the nature and importance of the disease. We have already described the symptoms which belong to atrophy of the optic nerve. The absence of these symptoms, that is to say, perfect integrity of the papilla, when the visual acuteness has been diminished for some length of time, is not frequently seen ; but in such cases we may expect recovery. Often, the signs of atrophy do not supervene till after the lapse of some time, and therefore we should be very cautious in our prognosis.

The mode in which amblyopic affections develop is very variable. It may happen, although rarely, that the disease supervenes suddenly, or is developed very rapidly. A few moments, hours, or days, suffice to establish a contraction of the visual field, central scotoma, or even complete blindness. These affections sometimes end favorably, sometimes the disease persists, and atrophy of the optic nerve ensues.

The prognosis therefore, as a rule, can only be determined in the course of the disease, and by a careful study of its progress. If there be no atrophy of the papilla, the prognosis is favorable, especially if the functional condition is stationary and improves, and if the phosphenes remain.

Much more frequently the visual disturbance develops slowly. In such cases, the disease takes several months before it becomes stationary, and, if the morbid cause remain, it may develop into progressive arnaurosis. Generally speaking, it may be said that, in the forms which are primarily favorable, the visual functions become weakened simultaneously in both eyes and to an equal extent. When the disease has been for a long time stationary, and when there is no atrophy of the optic nerve, we may even hope for complete recovery.

Amongst these forms, we may mention cases of amblyopia due to excess in alcoholic liquors and tobacco, habitual constipation, affections of menstruation, suppression of hemorrhoids, or of pathological and physiological secretions, venereal excesses, irregularity of sleep, or fatigue of the eyes from want of sleep. These causes act sometimes alone, but more frequently in combination. The more we succeed in accurately diagnosing the causes of the disease, and in removing or counteracting them, the more our prognosis will gain in precision.

The prognosis is more serious when there is room to suspect the presence of a chronic meningitis ; for, although active treatment often acts most bcneficially, not in frequently do we see this amblyopia change into degenerative amaurosis.

Disturbance of vision occurring in conjunction with acute and violent cerebral symptoms (encephalo meningitis) must be estimated according as the exciting cause of the affection is still in operation at the time of our examination, or has already passed off. In the latter case, if the disease has once become stationary, it may remain so, whatever be the form of the amblyopia or condition of the optic nerve.

On the other band, if the exciting cause is still in operation, our prognosis must be very reserved.

It is true that cases of complete blindness, secondary to cerebral disease, have been recorded, in which a part of the visual power returned after several weeks. But, as a rule, if blindness after an acute affection is prolonged, and if degeneration of the papilla is also present, no hope can reasonably be entertained. The most unfavorable prognosis belongs to those forms of amaurosis in which the vision of one eye is gradually lost and there is at the same time an irregular contraction of the field of vision and atrophic degeneration of the papilla, whilst there is an analogous diminution in the other eye, generally setting in before the first is lost. Having thus spoken of amaurosis and amblyopia in a general way, it remains for us to describe the special forms which these diseases assume.

  1. CONGEN1TAL AMBLYOPIA. DYSCHROMATOPSIA. ACHRO. MATOPSIA. Congenital amblyopia is found in persons whose eyes are absolutely normal in conformation, and in whom the ophthalmoscope does not reveal any anomaly. The diminution of the visual power may be more or less considerable, but it is absolutely stationary. The visual field is normal, as is also the color perception.

    The amblyopia often affects one eye only, and is so great that the patients cannot count fingers beyond the distance of a few paces. We also find in the eye affected an eccentric fixation. Again, many of these cases of monocular amblyopia are accompanied with strabismus.

    In other cases the amblyopia is present to a greater or less extent in both eyes ; yet, in these cases the diminution of the visual acuteness never attains the same degree as in cases of monocular amblyopia.

    A congenital deficiency in the perception of colors (Daltonism) may be partial or total. In total achromatopsia every color appears white or gray. In partial achromatopsia the eye fails to distinguish some particular color or its complementary color ; or it always confounds them with gray (romple te partial a, hromalo,6sia) ; or it may be able to distingiiish pure colors, but gets confused amongst shades of the same (partial incomplete achromatopsia, quantitative achroinalopsia, torpor of the chroinatic sense).

    Partial Achromatopsia. The most frequent form of partial achromatopsia is for red ; next in order comes achromatopsia for green, and the least frequent is for blue.

    Red Blindness (Ano~rythropsia Daltonisrri). In this form red appears as dark gray, its complementary tint as light gray. Cinnabar red is confounded with brown or green, purple with violet or dark brown. The red extremity of the spectrum is curtailed, and the entire speqtrum seems to be composed of two colors only viz., yellow and blue.

    Green Blindness (Achloropsia). Green is seen as blue or gray, as is also its complementary color, purple. We find that there is confusion between green and purple, and between yellowish green and red,. etc. The length of the spectrum is not diminished, but the green portion appears as gray, or is somewhat indefinite ; on its left the red or yellow is seen, on its right the blue.

    Blue Blindness (Akvanopsia) is very rare. It is characterized by an inability to distinguish blue and its shades; there is also a confusion between blue and yellow shades. The blue extremity of the spectrum is diminished.

    Great difficulty occurs in many cases in which we have to distinguish between red and green blindness and between blue and yellow blindness, symptoms of both of these deficiencies existing in the same individual. Thus we are disposed to admit simultaneous blindness for the complementary colors, and to call those cases red green blindness or blue yellow blindness.

    Total, Achromatopsia. In total achromatopsia the eye cannot distinguish any color or shade ; it only distinguishes variations in light and shade. The spectrum is curtailed on both sides.

    Congenital dyschromatopsia is much more common in men (3 5 per cent.) than in women (less than i per cent. in the latter). It is hereditary, and is transmitted on the mother's side, although she herself is not affected with it. In all cases of congenital dyschromatopsia the other functions of the eye are normal.

    The various attempts which have been made to remedy defects in the chromatic sense have had for their object to facilitate and increase by systematically exercising the power of color perception (Favre). It has also been proposed to use tinted glasses, chosen to increase the sensibility of the eye for certain colors, and to diminish it for others (Delbeuf, Spring). Either of these means is of great benefit where there is torpor of the chromatic sense; they are, however, of no avail in achroniatopsia, whether partial or total.

  2. AMBLYOPIA FROM WANT OF USE.

    Amblyopia ex Anopsia.

    It is generally admitted that when in early life, for some reason, an eye otherwise healthy does not participate in vision, the retinal sensibility becomes dull, and there is consequently a more or less pronounced amblyopia.

    This decrease of retinal sensibility seems to be in proportion to the duration of the period during which the eye has been inactive. In the first stage, central vision is more or less impaired, whilst peripheral remains normal.

    Later, the special sensibility of the fovea centralis is extinguished; the eye no longer fixes objects exactly, but moves about in an uncer┬Čtain manner, seeking to use the portion of the retina most favorable for vision. In the end, the fixation is definitely eccentric, or perhaps the visual acuteness is reduced to the perception of light.

    In many cases this form of amblyopia is followed by strabismus or nystagmus; but in other cases the deviation of the eye (monocular strabismus) is the origin of the impairment of the visual acuteness.

    Other causes which may prevent an eye from participating in binocular vision, and so bring about an amblyopia ex anopsia, are opacities of the cornea and cataract in early life.

    For these reasons it is not advisable to delay in making an artificial pupil in cases of congenital cataract, or in putting to rights any deviation of the eye. (See Chapter on Strabismus.)

    In cases where this form of amblyopia is slight, considerable improvement is always obtained by regular exercises. This improvement is almost certain in the first period of the disease, and at the beginning of the second. At a later stage, the result is negative.

    The exercise suited to the condition consists in making the amblyopic eye read, for a few minutes several times a day, large type, with the aid of magnifying glasses. As the vision improves, smaller letters and weaker convex glasses are used, whilst the duration of the exercise is increased.

    These exercises mav also be extended to the peripheral vision in the following manner: After having closed the healthy eye, we set up an object of medium size, a card for example, and move round this card various objects which the patient must try to see and recognize. The objects chosen at first are of considerable size, and are held very near the fixed card, so that the diseased eye can easily recognize them. By degrees they are brought nearer the limits of the visual field, and tire diminished in size Subcutaneous injections of strychnine have also given good results (Nagel). They may be used in conjunction with regular exercise of the eye, or alone when the full benefit of such exercise has been obtained.
  3. HEMERALOPIA.

    The characteristic symptom of this disease is inability to see except in a strong light. It is, therefore, apparent in the twilight, or after sunset, or when, in broad daylight, the patient is placed in darkness. The sense of light is considerably lowered, and the adaptation of the eye to reduce light very small (torpor of the retina).

    In good light the patients see perfectly ; their visual field is normal, as is also their color perception.

    As the intensity of the illumination is decreased, the central acuteness and extent of the visual field are also diminished. Sometimes eccentric vision is better than the direct. During the period in which the amblyopia is manifest, the color perception is also impaired. Simultaneously, dilatation of the pupils, loss of accommodation and weakness of the oculo motor muscles in general have been observed (A. von Graefe).

    All these phenomena are absolutely independent of the sun and moon ; they can be produced at will, by putting the patient in a dark place.

    The affection always attacks both eyes, but often in different degrees.

    Dryness of the conjunctiva (Habbenet) and white pearly patches near the margin of the cornea (Bittot) have been said to be characteristic of this disease. In cases of hemeralopia of sudden origin the ophthalmoscope reveals nothing abnormal, or at most a slight hyperaemia of the papilla. The result of the ophthalmoscopic examination is very different when the disease is a symptom of an affection of the deep membranes of the eye (consult article on Retinitis Pigmentosa).

    In the few cases where an autopsy has been made of persons affected with hemeralopia, considerable roughness of the ciliary ganglion has been found, with conges. tion of the vessels of the optic nerve.

    Progress and Termination. The course of acute hemeralopia is very characteristic. It comes on suddenly, and attacks at the same time a certain number of persons exposed to the same injurious influences (endemic or epidemic hemeralopia); it increases during the first days, and often disappears when the injurious surroundings are removed; if not, the disease may last for weeks or even for a few, months. Prolonged duration of the disease is most common in persons suffering from a relapse. It is very apt to recur.

    In all such cases, however, the disease ends favorably.

    Prognosis. The prognosis of acute hemeralopia is absolutel good; on the other hand, it is very serious when accompanied wit permanent disturbance of the vision or with gradual contraction of th visual field, as in retinitis pigmentosa.

    Etiology. Hemeralopia is especially common in spring, an amongst classes of the community exposed to the heat of the sun an night chills. Hence it is common among soldiers, sailors, etc. Thos who are weak and badly nourished are most liable to be attacked b it. Among sailors hemeralopia is often found along with scurvy; the officers enjoy almost absolute immunity from it.

    Again, epidemics of hemeralopia, due to a bad regimen and dazzling light, are seen in prisons and in educational establishments, as also i the southern provinces of Russia at the time of the prolonged fasts.

    All these facts tend to prove that hemeralopia is due to the prolonge action of bright light on a retina weakened by some general debilitatin cause.

    Treatment. Besides the remedies which are suited to the genera condition (clearing the gastrointestinal canal, administration of qu nine, iron, cod liver oil), it is of great importance to remove the patient from every injurious influence.

    The most rapid results are obtained by keeping persons affected with hemeralopia in a dark apartment (Forster, Dark Rooms of Netter For some time after, in order to prevent relapses, we must prote them from too strong a light by making them wear blue or smoke glasses. Epidemics of hemeralopia have been cut short by a contini ance of rainy or cloudy weather. Favorable results have been ascribe to instillations of pilocarpine or eserine (Galezowski).

  4. 4. ANIESTHESIA AND HYPER~ESTHESIA OF THE RETINA. OPTIC HYPER2ESTHESIA. ASTHENOPIA.

    Relinal an&,sthesia is characterized by a diminution of the centr visual acuteness, generally inconsiderable, rarely well marked; in son cases there is almost complete blindness. The visual field is alwa abnormal and very much contracted concentrically or irregularl True hemianopsia is very rare. Chromatic anomalies are, so to spea never absent ; sometimes the patient ceases to recognize some one more colors; sometimes the color blindness is absolute. The phc phenes are preserved.

    Functional examination rapidly fatigues the retina (Schweigger Spasm of the accommodation is often present. Some patients a relieved by the use of yellow glasses.

    There is also a certain h.rpenrslhesia of the retina, which, in hysterical subjects, often attains considerable intensity, or may be manifested only by slight photophobia. In such cases the patients see best through dark colored glasses, or in feeble light, and the visual field is then enlarged.

    The optic papilla preserves its normal aspect, even although the disease is of long duration.

    The disease is almost always found in both eyes, but in different degrees.

    Progress and Termination. This affection is suddenly developed, or attains its maximum in the course of a few hours or days. Sometimes it remains stationary for a certain time; more frequently recovery is complete at the end of a few weeks. In a few isolated cases recovery is not perfect, especially when the general health is not restored to the normal conditions (in hysterical patients).

    The prognosis is therefore, as a rule, favorable.

    Etiology. Retinal anesthesia almost exclusively affects women and children. It is observed in conjunction with cutaneous anesthesia (hemianoesthesia) or with muscular spasms, in persons of a generally irritable disposition, and under the influence of psychical excitement. It is especially apt to attack people who are nervous, anemic, or hysterical, or who are convalescent from some serious disease, such as scarlatina, measles, typhoid fever, etc.

    Treatment. Patients must be placed for a few days in an absolutely dark room, and, beginning with the sixth day, the light must be gradually increased. When the patients go out, different shades of blue glasses must be prescribed. Afterwards, when anaesthesia prevails, the use of yellow glasses is often successful. The internal administration of the preparations of zinc in increasing doses (1 1/2 to 4 1/2 grains of zinc lactate daily) and bromide of potassium (15 to 45 grains daily) have been recommended.

    Absolute rest to the eyes, strengthening diet, aromatic and saline baths (hydrotherapeutics), complete the treatment.

    Good results have also been obtained from the subcutaneous injection of strychnine, from inhalation of nitrite of amyl, which must be very carefully used, and from the constant current.

    Retinal anaesthesia of hysterical origin may be effectively treated by metallo therapeutics (Burq, Charcot). When we have ascertained which metal, on being applied to the forehead, causes the amblyopia and dyschromatopsia momentarily to disappear, strips or plates of it should be kept on for a considerable time, and along with this we administer the preparations of the same metal internally.

    Hyperesthesia of the optic centres presents itself with tile following characteristics : hi slight degrees the patient is tormented with the persistence of retinal impressions (secondary images and complementary colors). The more serious cases are characterized by dazzling, muscae volitantes, luminous impressions, more or less intense, chromopsia, and dreadful hallucinations. These phenomena co exist either with a normal or an amaurotic state of the vision, and are sometimes accompanied by ciliary hyperoesthesia, lachrymation, and orbicular spasm.

    This affection has been attributed to the irritating action of an intense light ; for example, the light reflected from a large expanse of snow illuminated by strong sunlight ; or to sudden variations of illumination. It may also come on when the eyes have been used for a long time on very bright objects. At other times, the hyperoesthesia seems to be due to a cerebral affection (prodromata of insanity) and to the prolonged use of certain narcotics. Sometimes it is one of the symptoms of hysteria or hypochondriasis.

    Treatment. The eyes must be kept absolutely at rest, by the patient either remaining in a dark room, or wearing dark colored glasses. Congestive states of the brain require saline purgatives', cooling drinks, and even local blood letting. In a case of complete amaurosis accompanied by optic hyperaesthesia, which resisted all other means, von Graefe divided the optic nerve, which completely relieved the patient.

    Retinal Asthenopia occurs chiefly as a defect of visual energy, the vision being otherwise healthy. In some persons we find that although we carefully correct any existing anomaly of refraction and accommodation, as also any insufficiency of the internal recti, they are still unable to use their eyes for their ordinary occupations, although their visual acuteness is normal. Severe pains in the eyes, with dimness of vision, always come on, and sometimes very quickly. Blue or smoked glasses are without effect, but in some cases yellow glasses afford immediate and lasting relief. Santonin, which has been recommended, is of no benefit, and the same remark holds true regarding the instillation of pilocarpine.

    5. TOXIC AMBLYOPIA.

    1. The most frequent form of toxic amblyopia is due to excesses in alcoholic drinks and the use of tobacco.

      This form is characterized by a more or less considerable diminution of the central visual acuteness (central scoloina), whilst the visual field retains its integrity. The scotonia is usually oval in shape, its long axis being horizontal, and (extend,, from the fixation point towards the blind spot patients often tell us that they see better by reduced than by strong light. The color perception is impaired in the neighborhood of the scotoma.

      In the early stages of such affections the ophthalmoscope does not reveal any alteration in the fundus of the eye; later, we find a wellmarked hyperoemia of the nasal half of the optic papilla, and a paleness of the temporal half. Again, we may find signs of nerve atrophy.

      The disease almost always affects both eyes to a nearly equal extent. It attains its acme very slowly, remains stationary, and passes off if the patient is protected from every injurious influence before the disease is very far advanced. In such circumstances, and under proper treatment, vision may be completely restored.

      On the other hand, relapses are frequent if the patient is again exposed to the original injurious conditions. The relapse may assume a more serious form of amblyopia, and terminate in progressive atrophy. The disease is due to chronic retro bulbar neuritis (see P. 297).

      Prognosis. So long, therefore, as there is no alteration in the optic papilla, and so long as we are able to remove the patient from every injurious surrounding or bad habit, the prognosis is exceedingly favorable. The chances of complete recovery diminish with the duration of the disease and with the appearance of atrophic symptoms in the optic papilla.

      In our treatment we should take into account all the aetiological conditions. The disease sometimes yields if tobacco and alcohol be absolutely interdicted, and the patient's mode of living regulated both as regards food and sleep. In order to hasten recovery and make it more certain, we may beneficially use, according to the general constitution of the patient, either local blood letting, or diaphoretic or aperient remedies. Yet, amblyopia from excesses in alcohol and tobacco most frequently occurs in persons who are weak and badly nourished, and whose general condition prevents any enfeebling treatment, and requires rather such remedies as will stimulate their vital forces. Often it is beneficial, after a favorable change has set in, to stop all remedies, and to resort to them again only if the favorable progress of the disease is interrupted. The internal administration of potassium bromide, and subcutaneous injections of strychnine, seem to be of use in chronic cases.
    2. Amblyopia from lead poisoning. It also affects both eyes simultancously, and is often so rapidly developed that in a few days the amaurosis is almost complete, the pupils being widely dilated. In other cases the disease develops slowly, and begins with central amblyopia without any contraction of the visual field. Sometimes with the ophthalmoscope we'find no visible alteration of the fundus ; more frequently we flind changes which resemble those of albuminuric retinitis and optic neuritis (choked disc) ending in atrophy of the papilla. In our treatment of this form of amblyopia, we must follow the general indications afforded by lead poisoning (iodide of potassium, injections of morphine, milk diet).
    3. Uramic amaurosis. Along with the other symptoms of uremia, such as headache, fever, faintness, dyspnea, vomiting, syncopy, convulsions, and coma, there is a sudden diminution of the visual acuteness, which in a few days may almost amount to complete blindness. Inmost cases the vision speedily returns, but not always in a regular manner. With the ophthalmoscope nothing is seen, except, perhaps, slight edema of the papilla and of the surrounding retina (Schmidt Rimpler).
    4. AmbNspia supervening after large doses of quinine is very rare, and is almost always transitory (like the buzzing in the ears and the deafness). Cases have been recorded in which the disturbance of vision persisted, and even a few cases in which there was complete blindness with pallor of the optic papillae, smallness and scarcity of the retinal vessels. Salicylic acid in large doses has also caused analogous impairment of vision (Riess).

      We may here state that any circumstance which produces general debility may give rise to a diminution of the visual acuteness. Severe epistaxis, repeated menorrhagia, prolonged suppuration, profuse secretion, or prolonged lactation, may be counted amongst such causes. In these cases it often suffices to remove the cause, and strengthen the patient's system, to arrest the disease and procure a steady improvement. If, however, we find on ophthalmoscopic examination some disturbance of the nutrition of the nerve, we must be very guarded in our prognosis.

    6. AMBLYOPIA FROM CONCUSSION OF THE EYEBALL AND FROM REFLEX ACTION.

    We place these two classes of amblyopia in the same group, for the impairment of vision which characterizes them has not as yet been explained. Thus, we have seen that after Some shock to the eyes, as by the passage of a projectile before them a blow from a fist or the cork from a bottle the visual acuteness is very much diminished, and there may even be complete blindness. At first, the ophthalmoscope may not show any change; later, we may find atrophic degeneration in the optic nerve. In these cases subcutaneous injections of strychnine have been very highly recommended.

    The so called reflex amaurosis has been observed in connection with lesions or prolonged irritation of the fifth pair (supra orbital and dental nerves, etc.). Thus, in these cases we have seen tile disease arrested, and even the vision improved, by the excision of frontal cicatrices which involved the supra orbital nerve, as also after the extraction of decayed teeth.

    7. HEMIANOPSIA.

    A symptom which frequently accompanies migraine and gastralgia consists in the sudden and transitory suppression of one half of the field of vision (visus dimidiatus, aniaurosis partialis fugax of Forster). This phenomenon sometimes lasts some minutes, a quarter of an hour, or longer, and is generally accompanied with luminous apparitions (scintillating scotomata), which occupy the patient's attention to such a degree that he does not observe the hemianopsia. These attacks appear at irregular intervals, sometimes for the whole life, but with diminishing intensity and frequency in later years. During the intermissions between the attacks the vision is quite normal. The hemianopic and transitory character of the disease indicates that it is due to a limited central ischemia. Some observations show complication with disturbance of speech, hemiplegic weakness, and other symptoms of a persistent central disease (Charcot). Usually we prescribe bromide of potassium and other remedies used in migraine, such as quinine (metallotherapeutics). The attack is sometimes shortened by a dose of alcohol.

    In true hemianopsia one half of the field of vision in each eye is blind. Most frequently the half of the visual field which is defective is situated in both eyes on the same right or left side (lateral homonymous hemianopsia, right or left) ; more rarely it is crossed, so that the nasal or temporal half is wanting in each eye (internal nasal, or external temporal hemianopsia).

    1. In homonymous hemianopsia (right or left) there is always a very distinct line of demarcation separating the corresponding blind halves of the two retinae on which the disease depends, from the halves in which the vision is preserved. The line does not, in general, pass through the point of fixation, which, therefore, is included in the half preserving its vision. The visual acuteness of this point remains normal, and its chromatic sense is not disturbed.

    The ophthalmoscopic appearance of the nerves does not show any alteration, even after the hernianopsia has lasted for a considerable time. Von Graefe, however, observed a case of atrophy of the papilla, limited to the corresponding half of the nerve with retinal anesthesia.

    Hemianopsia commonly comes on suddenly and remains stationary ; in some cases, however, it is developed in the course of a few weeks, and the progressive blindness for colors in tile affected part of the visual field precedes the hermianopsia. It may remain always at tile same point, but also the condition may improve, and there may even be complete recovery. When the fixation point escapes the deficiency, vision is little interfered with. Reading and writing being executed from the left to right, the right hemianopsia is much more felt than the left ; the patients counteract it by turning their heads sideways.

    The explanation of this defect in the visual field is to be found in the semi d ecussation of the optic nerves in the chiasma (Fig. 93). The right optic tract (r. t.) supplies fibres to the temporal side of the right eye and nasal side of the left. Any lesion of this tract will, therefore, produce 1 e f t hernianopsia. Right hemianopsia is simply explained by a lesion of the left optic tract (I. t.).

    Crossed temporal hernianopsia can only depend on some cause which acts on the nerve fibresas they cross in the chiasma; nasal hemianopsia on multiple lesions acting on both tracts.

    The prognosis can only exceptionally admit the restitution of the deficiency, but, so far as the danger of blindness is concerned, is absolutely good. Blindness can only supervene if there is some lesion of the other optic tract or some new intracranial affection. In cases where chiasma is implicated and the affection a progressive one, such as a tumor, complete blindness may result.

    Etiology. The most frequent cause of these various forms of hemianopsia is cerebral hemorrhage or some circumscribed focus of inflammation, periostitis, tumors, embolism, and injuries. It occurs equally in affections of the corpora geniculata or quadrigemina, the optic thalamus, the pulvinar, the fibres of Gratiolet, and the cortical ,substance of the occipital lobe. It is here that the optic tract of the me side takes its origin, and wounds of this optic centre produce hemianopsia, as we have learned by the interesting experiments of unk, which have been confirmed by some pathological (Westphal) and clinical (Schmidt Rimpler, Nieden) observations. Munk believes at the cortical centre, receiving the sVmmetric retinal impressions both eyes, includes also the visual centre, that is to say, the region here the visual perceptions are transformed into notions. Therefore, ness of the visual centre involves also tile loss of the notions accumulated this region by time and experience, so that an object may be seen without awaking the notion of its signification or use. this has been called mental blindness (Seelenblindheit) ; we think that it would be better to call it loss of the visual memory, visual amnesia.

    Hernianopsia may be accompanied with hemiplegia, hemianestbesia of the same side, and aphasia if the deficiency is on the right hand side.

    In a few cases we find hemianopic deficiencies of the superior or inferior portions of the visualfield, which are without anatomical explanation. When they are clearly defined, and when, at the same time, the acuteness of the central vision is nearly normal, they do not forebode progressive amaurosis.

    2. Temporal hemianopsia (external) is characterized by the absence of vision in the external half of each eye. Still, in this form, the defect is never so exactly limited to the median line as in homony hemianopsia. There is always a transition zone between the defective part of the visual field and the part which still preserves its usual acuteness.

    These forms sometimes come on suddenly and symmetrically in both eyes. At any moment the condition may become stationary, recede, and even completely disappear. But the defect may also gradually extend to the opposite half of the visual field and lead to complete blindness.

    Therefore, the prognosis in such cases of hemianopsia should be very reserved, as we are unable, especially in the early stages, to distinguish the progressive forms from those which are more favorable. The latter are characterized by rapid and symmetrical development in both eyes, by the relatively good central visual acuteness (1/4 or 1/6) and by the perfect integrity of the optic papilla, even although the disease is of some duration.

    Etiology. The most frequent cause is tumor, or some localized inflammatory affection, at the base of the brain. Anything in this region which is developed immediately in front of or behind the chiasma will, first of all and by preference, affect the crossed nerve fibres, which circumstance explains the anesthesia of the internal portions of both retinae.

    3. Nasal hemianopsia (internal), that is to say, blindness in the nasal portion of the visual field of each eye, can be produced only by a disease on both sides of the chiasma or on the external side of both optic nerves. The condition is of doubtful existence.

    There is nothing special as regards the eye in the treatment of hemianopsia. The central cause, to which the anomaly of the vision is due, can alone furnish us with indications.

    8. SCOTOMATA.

    This name is applied to interruptions of the continuity of the visual field. These interruptions are situated at the centre of the field of .Vision (central scotoma) or towards its periphery (eccentric scotoma).

    Again, the scotoma is either well defined, or there is a diminution of the visual acuteness in the surrounding parts. In cases of central scotoma, the acuteness of vision may be so reduced that the patient,instead of using the centre of the retina, prefers to use an adjacent portion (eccentric fixation).

    In such cases, ordinary examination suffices for purpose of diagnosis. In other cases, the central vision has not suffered so severely, and the diagnosis is then greatly assisted by the examination of the color perception (Leber). Thus, the patients do not distinguish colors in the part of the visual field corresponding to the scotoma, which they perfectly distinguish in the unaffected portions.

    Along with central scotoma, the periphery of the visual field may be absolutely normal, or there may be a more or less irregular contraction.

    Again, central scotomata may either come on suddenly or take several weeks or months to develop ; they affect both eyes simultaneously or successively. During the period of development, they may extend outwards, or there may be a general diminution of the visual acuteness which becomes,. by degrees, limited to the central region, and assumes the form of a scotoma.

    If the disease, toxic central scotoma excepted, has once been stationary for a few months, there is little chance of its extending at a later period ; but we can no longer hope to restore vision in the anesthetic portions of the visual field.

    Eccentric scotomata are often situated symmetrically in both eyes. If the peripheral vision, in the parts near the scotoma, is perfectly normal, there is no fear of blindness. If otherwise, the disturbance of vision often indicates the beginning of an amaurotic affection. The examination of the color sense in the neighborhood of the scotoma is very important ; for, as long as the perception of colors is normal, the extension of the scotoma is not imminent.

    To the ophthalmoscope the optic papilla and retina sometimes seem to be absolutely normal; but more frequently there are symptoms of optic nerve atrophy.

    Prognosis. Except in the case of toxic central scotoma the vision rarely improves or regains its normal condition. If the scotoma has been present for some time and if the periphery of the field of vision is normal, the prognosis is favorable, in so far as there is no danger of blindness. When the eccentric vision (apart from the scotoma and not in connection with it) is diminished, the disease has then the characteristics of progressive amaurosis.

    Etiology. The cause of these scotornata is rather obscure. They are due to circumscribed alterations in the cerebral terminations of the optic nerves, or to a retro bulbar neuritis. The disease sometimes seems to be hereditary.

    Treatment. Since there is this uncertainty, the treatment should be adapted to the constitution of the patient and to the conditions which seem to have determined, or which accompany, the disease. Local blood letting, revulsives, diaphoretics, aperients, are sometimes useful. In other cases, benefit is obtained from tonics, iron, hot baths, residence in the country, etc. Iodide of potassium, lactate of zinc, nitrate of silver, have also been recommended, as also injections of strychnia, and the constant current.

    The cerebral and spinal forms of amaurosis have been discussed in our chapter on Degeneration of the Optic Nerve. It remains for us to indicate the means which are employed for the detection of a simulated amaurosis.

    SIMULATED AMAUROSTS.

    Pretended blindness in one eye may easily be detected by a prism placed with its base upwards or downwards before the admittedly healthy eye, while the patient is made to look at a black point on a piece of paper. If he says that there are two points, it is evident that he sees with both eyes.

    We may also place before the healthy eye a prism, so that its base crosses horizontally the middle of the pupil ; in that way it produces monocular diplopia, and convinces the malingerer that he has diplopia with his good eye alone. Then we open his other eye and push the prism upwards or downwards, so that it covers now the whole pupil. Diplopia would be produced now by the vision with both eyes, and, when two images are seen, simulation is sure.

    Another method consists in placing a prism of 10 or 15 degrees with its base outwards before the eye said to be blind. If it sees, it will turn inwards for the sake of single vision, and we will also observe the movement of readjustment outwards when the prism is withdrawn (de Weltz). An eye really. deprived of vision will not move, as binocular vision no longer exists. Ordinary stereoscopes, with prismatic lenses or with mirrors (Flees's apparatus), are very useful in discovering pretended monocular blindness.

    Another good method of detecting simulation is the use of Stilling's black sheets, on which letters are printed in various colors. These letters become invisible when looked at through a glass of a determined color, thus red letters are invisible if looked at through a green glass, etc. A great variety of these tests can be obtained in drawing upon ordinary white paper signs or words with red and blue pencils or inks, which become invisible to the eye provided with a red or blue glass (Bravais).

    To avoid any error, the surgeon will do well, first of all, to ascertain what takes place for his own eye; then he should place the same glass before the good eye of the person whom he is examining, the other eye, which is supposed to be blind, being kept open.

    If the person reads all the letters, the simulation is evident.
    Simulated amaurosis of both eyes can only be detected by careful observation of the movements of the pupils, and by taking into consideration the mode of the pretended development, compared with the results of ophthalmoscopic examination.


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