Chapter VIII The Vitreous Body | Operating Microscopes

Anatomy. The vitreous body occupies the entire space of the cavity of the eyeball comprised between the posterior surface of the lens and the retina. It is exactly adapted to this cavity, being convex posteriorly and to the sides, whilst anteriorly there is a slight depression in which the lens is lodged.

The vitreous humor is a clear, perfectly transparent mucoid substance. It is enclosed in a very thin vitreous membrane, the hyaloid membrane, which is united to the neighboring structures at two places only, viz., at the ora serrata near the zonule of Zinn, and at the optic papilla.

The histological structure of the vitreous body is but imperfectly known ; according to some authorities, its substance is perfectly homogeneous, and does not contain any formed material. Still, the fact that foreign bodies may be encysted in the vitreous body, and the transformations which it undergoes when laid bare, seem to point to the presence of a cellular stroma. Brucke thought that he recognized the presence of several concentric membranes, and Hannover believed that there are numerous membranes dividing the vitreous into segments like an orange. All such formations, as also the star shaped cells of the vitreous body, observed by several anatomists, are thought by others to be artificial, depending on the method employed in the histological preparation of the tissue. According to Ritter, the surface of the hyaloid membrane, which is next to the vitreous, is covered with a very delicate epithelium. Stilling, again, finds a central canal having a diameter of 2 millimetres. This canal becomes wider as it approaches the optic nerve, where its opening exceeds by 2 millimetres the diameter of the papilla.. Stilling has also been able to distinguish a cortical substance, which nearly occupies the peripheral third of the vitreous body (in concentric layers), and a star shaped nucleus which has three rays, similar to the nucleus of the lens.

The vitreous body has neither vessels nor nerves. It derives the materials for its nutrition and reconstruction from the uveal tract.

DISEASES OF THE VITREOUS BODY.

ART. I. Inflammation of the Vitreous. Hyalitis.

Idiopathic inflammation of the vitreous body was long contested it has only been admitted since we have been able to observe with the ophthalmoscope the changes which take place when a foreign body is introduced into the vitreous humor. At first we notice a slight haze round the body, which grows thicker, and finally hides it from our view. St the same time other filamentous or flaky opacities are formed in other portions of the vitreous. If circumstances allow us to watch the ulterior evolution of the phenomena, we find that the grayish opacity surrounding the foreign body assumes a yellowish color, which gradually extends to the surrounding tissue, and, if situated immediately behind the lens, may change the appearance of the pupil.

Again, we may be able to observe suppurative inflammation of the vitreous body after excision of corneal staphylorna or the extraction of cataract by flap operation. In such cases purulent infiltration of the vitreous takes place very rapidly.

The course of these alterations is very variable. Sometimes there is an abundant formation of cellular tissue which becomes vascular, and the vessels of which communicate with those of the deep structures of the eve. At a later stage, this tissue contracts, and may thus cause separation of the retina. In other cases, as, for example, when a foreign body is encysted, the formation of the cellular tissue is limited to a circumscribed area. But it is especially after affections of the choroid and ciliary body that we have an opportunity of observing the alteration of the vitreous body, and the symptomatology of the suppurative inflammation is precisely that of suppurative choroiditis and cyclitis (see P. 225). We would refer to the chapter on the treatment of these affections for the treatment of inflammation of the vitreous body.

ART. II. Opacities of the Vitreous Body.

The form of these opacities is very variable :

Sometimes, in the midst of the vitreous body, which is otherwise perfectly transparent, we see well defined opacities, with very fine prolongations, which remain almost immobile Generally only a few are seen, almost always situated in the neighborhood of tile optic nerve We find them secondarily to retinitis, or in cases of posterior staphyloma or, in elderly persons, without any other alteration of the eye (Shweigger).
In other cases, the opacity of the vitreous is in the form of a very fine or dotted veil which is spread out in front of the fundus of the eye. It presents to the ophthalmoscope a somewhat diffuse appearance, which may be confounded with the haze of retinal edema. This form of opacity occurs especially in syphilitic affections (retinitis and choroiditis).
The most frequent form is that of mobile, filamentous, or membranous opacities. They are easily recognized with the ophthalmoscope, when the patient moves his eye rapidly. The rapidity with which these opacities move, and the extent of their excursions, may give us some information as to the degree to which the vitreous humor has become liquid. Those opacities are chiefly seen after hemorrhages or diseases of the deep membranes of the eye (cyclitis and choroiditis). Still, there is nothing to prevent such opacities forming after idiopathic alterations of the vitreous body.

The disturbance of vision depends on the shadows thrown by these objects on the retina.

If that membrane be very sensitive (hyperesthesia of the retina), and especially if the look be directed on some well illum in ated surface, the eye, even in normal state, easily perceives a great variety of small opaque bodies (globules isolated, or strung together, curled up filaments, etc.), which have been called moving scotomata or musca, volitantes (myodesopsia). These phenomena are a great source of annoyance to many patients. Still the museev volitantes have no importance when the visual acuteness is normal, and when, on ophthalmoscopic examination, we do not find any real opacity of the vitreous body.

Real opacities of the vitreous influence the vision in very different ways. Diffuse opacities more or less veil the entire visual field ; flaky or membranous opacities, when extensive, may so intercept the luminous rays as to destroy vision for small objects. The patient then gets into the habit of moving his eye abruptly so as momentarily to free the central part of the visual field ; but soon the opacities regain their former position, and the visual field is once more obscured. These movements are often repeated by the patient (as when he wishes to read), and this symptom is, therefore, very characteristic of the disease which we are discussing.

We can easily obtain information from the patient as to the details of these opacities of the vitreous, by using the endoptic test. For this purpose, the patient must look on some bright surface through a very small opening pierced in a card. A strong convex lens placed before the eye will aid him in seeing the opacities.

The cause of" these opacities must be especially sought for in those affections of the ciliary body or of the choroid which in various ways bring about this alteration of the vitreous body:

By disturbance of its nutrition, or by inflammatory irritation.
By different kinds of effusion: : serous, purulent, but especially hemorrhagic. Effusions of blood may also result from injury, from a blow on the eye, from extraordinary muscular effort, as in violent coughing or vomiting, or, again, from congestion of the eye due to a sudden cessation of hemorrhoidal or menstrual discharge, or in diseases of the heart and the blood vessels. The effused blood may occupy the entire vitreous body, or only a portion of it ; after a short time it sinks to the bottom of the vitreous and becomes absorbed. Long afterwards we can still see with the ophthalmoscope flaky opacities, the mobility of which corresponds with the fluidity of the vitreous.

The prognosis varies with the nature and origin of the opacities. When they are due to hemorrhage, without any serious disease of the choroid, and the vitreous is otherwise healthy, they may be absorbed. But generally opacities of the vitreous remain, and do not completely pass off. Disturbances of the general circulation are likely to occasion relapses. We must also remember that in cases of myopia, opacities of the vitreous often precede separation of the retina, and that in other cases separation of the retina may follow the contraction of the newly formed cellular tissue in the vitreous body. Purulent effusions (abscess of the vitreous body) usually lead to the loss of sight.

Treatment. Very often the treatment is that of the choroidal or relinal affection, of which the opacities are a consequence. In cases where the effusion arises from general disturbance of the circulation or local injury, it maybe necessary to apply the artificial leech of Heurteloup to the temple, to keep cold compresses on the eye, to use foot , and to enjoin absolute rest. We must also take into account any special indications, 'such as hemorrhoidal discharge, menstrual disturbances, etc.

To aid the absorption of the opacities, we may produce diaphoresis by means of injections of pilocarpine ; we may also give laxatives, corrosive sublimate, iodide of potassium ; hot compresses often seem to act favorably. We have obtained very good results from repeated paracentesis of the anterior chamber with slow escape of the aqueous humor, especially in the common case of persistent opacities of the vitreous humor accompanying posterior staphyloma. The constant current has also been recommended for the rapid absorption of these opacities (Girami Tcuion, Lefort).

In one case, Von Graefe obtained a great improvement of the visual acuteness by lacerating and displacing membranous opacities of the vitreous with a needle.

ART. III. Fluidity of the Vitreous Body, Synchysis.

The vitreous body may lose its normal gelatinous consistence, and become more or less fluid (synchysis of the vitreous body). Often, only a portion of the vitreous body (anterior or posterior) is thus affected. The synchysis can only be diagnosed with certainty when there are also present opacities of the vitreous, which, by the rapidity and extent of their movements, may indicate to us the degree of fluidity of the medium in which they float.

Softness of the eyeball has wrongly been cited as a symptom of this affection, for while it is true that there is almost always a fluid vitreous in such eyes, yet the disease is often observed in eyes which have rather an increased tension.

Tremulous iris, especially at the periphery, is also said to be a symptom of the disease which we are discussing, but is not immediately due to it, but to the fact that the iris has lost the point of support on which it should rest. This symptom, then, merely indicates that the same circumstance which has produced softening of the vitreous has also caused displacement of the lens (from rupture of its suspensory ligament).

Partial fluidity is chiefly met with in cases of sclerotic ectasia, and in that portion of the vitreous which is next to the ectasia. General liquefaction of the vitreous body is also observed in staphylomatous eyes, as also after effusions, after dislocation of the lens, after loss of a portion of the vitreous, and, again, where there is some affection of the deep structures (choroiditis).

A very remarkable phenomenon is produced by the presence of cholesterine crystals of tyrosine and of phosphates (Poncet) in the midst of the vitreous body. With the ophthalmoscope we then see numerous bright shining bodies, which become endowed with rapid movement whenever the eye moves, and gradually sink to the bottom of the vitreous when the eye is fixed (scintillating synchysis). These crystals may be found in a transparent vitreous, or they may be mixed with other filamentous opacities, to which they may be adherent. Their origin is not exactly known. They are also met with in the lens, in the retina, and between the retina and choroid, and in perfectly healdly eyes notably in those of aged persons.

ART. IV. Foreign Bodies in the Vitreous Humor.

When a foreign body, such as a fragment of lead, iron, stone or glass enters the vitreous humor, and the lesion of the parts which it pierces before being brought to rest is not such as to prevent an examination of the media of the eye, we can, at least for a short time after the accident, diagnose its presence either with the ophthalmoscope or the endoptic test, or, again, by the functional conditionespecially by the examination of the field of vision. After some time, it is often lost to view in the inflammatory disturbance which its presence excites, or it becomes encysted by a membrane, through which it can for some time still be recognized by its characteristic reflection, or it sets up immediately a suppurative hyalitis.

If once encysted, the foreign body may sometimes remain for a long time even to the end of life without occasioning any disturbance. Yet this immunity of the wounded organ is never sure, for it is often lost by inflammation at a period long after the accident (probably from displacement of the encysted body).

Again, it must not be forgotten that the presence of a foreign body in one eye threatens the other eye with sympathetic inflammation.

For these reasons, it is always important, when a foreign body has entered the vitreous, to ascertain if it cannot be extracted. If we are fortunate enough to find it still in the lips of the wound, we may extract it, enlarging the wound if necessary, then applying a pressure bandage, and following such a course of treatment as the lesion seems to demand (cold compresses, atropine, etc.).

If the foreign body has already entered the eye, and if, on account of its nature and the danger its presence involves to both eyes, we decide to operate, we must make sure of its exact position with the ophthalmoscope, and by carefully examining the surface of the sclerotic with a probe.

If we find a spot which is specially painful, the foreign body is most likely in the corresponding part of the vitreous (von Graefe). Moreover, the situation of the external wound, the course of the foreign body, and careful probing of the wound should aid us in our diagnosis.

Method of Operation. At the spot where it is believed the foreign body may be most easily reached, a meridional incision from I to 1 5 centimetre in length should be made through the sclerotic to the vitreous, mid in attempt made to seize the object with a blunt hook or forceps.

III the case of a fragment of iron, the extraction should be performed with the electro magnet (Hirschberg's), by means of which success is often attained even when the object is invisible, and its exact position unknown. It is sometimes necessary to reinsert the magnet several times, or to change the pole, as the fragment may itself have been magnetized in forging. After the operation, the sclerotic wound may be closed by a suture.

The cases in which vision has been partially or wholly preserved by the aid of this instrument are so numerous that its use is expressly indicated. If a traumatic cataract exists as the result of the injury, extraction may be made, and the magnet inserted into the corneal wound and through the pupil. Should the operation be unsuccessful, it will then become necessary, in order to prevent sympathetic affections in the other eye, to practice enucleation, or evisceration.

The operation which we have just described is also available in cases where the lens, being dislocated into the vitreous, becomes the starting point of an inflammatory affection of the eye, which, by its influence on the general health or on the other eye, may render surgical interference necessary. We may attempt its removal by a simple sclerotic incision according to the prescribed rules, or by a peripheral linear incision of the cornea with iridectomy, using a curette or a blunt book (Fig. 94) to draw the lens out of the eye.

Cysticercus of the Vitreous Body. When we have an opportunity of watching the development of the cysticercus before it enters the vitreous body, we find in the fundus a bluish gray opacity situated between the retina and choroid. This opacity increases in extent and density, and the retinal vessels at this point gradually grow dimmer till they become imperceptible. Then the grayish opacity extends forwards to the hyaloid membrane, and a small cysticercus vesicle is detached, which enters the vitreous body. At other times, the vesicle is placed below the retina, causing separation ; it then perforates that membrane, and escapes into the vitreous humor.

To the ophthalmoscope, cysticercus of the vitreous body appears as a bluish gray transparent vesicle, showing at its periphery a clear, slightly reddish (hydatic) reflection ; occasionally the head and neck of the cysticercus are to be seen, as they sometimes advance out of, and retract into, the vesicle.

At a later period, the diagnosis of cysticercus may be rendered difficult by opacities of the vitreous body. These opacities are characteristic : they appear as a system of curtains or multiple veils, their folds presenting themselves to the ophthalmoscope as furrows or deep strie, the configuration of which varies with the movements of the eye.

The visual disturbance at first consists of a well defined, fixed interruption of the visual field, in the form of a black globe, but at a later stage there is in addition a more extensive cloud.

If the disease is left to itself, it leads to chronic irido cyclitis with periodical exacerbations, and ends in atrophy of the eyeball. Sometimes there may even supervene a purulent panophthalmitis with exophthalmos.

Two cysticerci have been observed to exist in the same eye, but the presence of a cysticercus in both eyes of the same individual has not been noted. The presence of cysticercus does not seem to render the other eye liable to a sympathetic disease. Cysticercus of the vitreous body is very common in the North of Germany, but rare in the South of Germany, in England, Switzerland and France. The natural course of this disease having been always disastrous, the extraction of the cysticercus is undoubtedly indicated, and should be attempted as soon as possible, even though the object be imbedded under the retina.

The best results accompanied by preservation of the sight have been obtained by Alfred Graefe, who has also constructed an ophthalmoscope for the special purpose of determining the precise location of the cysticercus. This being done, he makes at that point a meridional incision in the sclerotic, as in the operation for detachment of the retina, if the cysticercus is implanted under the retina, or directly into the vitreous.

Sometimes the cysticercus appears at once ; if not, it has to be drawn out with forceps. Should suppurative inflammation supervene, enucleation must be resorted to.

ART. V. Persistence of the Hyaloid Artery.

During intra uterine life, as is well known, the hyaloid artery crosses the vitreous body from the papilla of the optic nerve to the hyaloid fossa. This artery disappears at the end of fatal life.

In very rare cases it persists throughout life. It is seen as ail opaque cord, surrounded with a second, somewhat grayish, zone (Saemish) ; with focal illumination, some have even tbought that they observe a red color in the cord, along with undulatory movements (Zehender). The persistent artery has also been seen to be attached to a dislocated cataract (Wecker). Lately, we observed such a case where the cord began on the papilla as an irregular grayish opacity occupying the upper half of the optic nerve and the surrounding retina ; it crossed the vitreous body outwards and downwards, and was attached to the lower half of the capsule, which it enclosed in a concave opacity. The same eye had also remnants of the pupillary membrane in the form of filaments beginning on the anterior face of the iris and uniting into a central pigmentary spot upon the capsule. The patient could, with this eye, count fingers at i metre's distance.

ART. VI. Separation of the Vitreous Body.

This separation has been observed and demonstrated anatomically by Iwanoff in eyes which had sustained injury and in myopic eyes. In cases of posterior staphyloma, the injured vitreous retracts, and detaches itself from the byaloid membrane, which remains adherent to the retina (Duke Charles of Bavaria). The ophthalmoscopic character of this disease remains as yet undecided.

Galezowski claims to be able to recognize it, at least in the direct image, by the existence of a gray crescent surrounding the papilla at a little distance from it.

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Chapter VII Amblyopia And Amaurosis