VITREOUS

From Big Medical Encyclopedia

VITREOUS [corpus vitreum (PNA, JNA, BNA)] — the translucent jellylike mass filling space between a back surface of a crystalline lens, a flat part of a ciliary body and a retina (the vitreous camera). Page of t. is constant structure of an eyeglobe, does not regenerate and it is replaced at loss with intraocular liquid (watery moisture. T.).

Embryology

Primary S. of t. begins to form at the end of the 3rd week of pre-natal development from a small amount of the mesenchymal cells which are available between a rudiment of a crystalline lens and an internal wall of an eyecup. Further from the mesenchyma getting into a cavity of an eyecup through a secondary germinal palpebral (vascular) fissure the rich vascular network C. of t develops. After closing of a germinal crack of an eye the leg of an eyecup begins to be differentiated, the artery of a vitreous (a. hyaloidea) feeding S. with t is formed. and crystalline lens. This artery passes in the kloketovy channel (the vitreous channel, T.; canalis hyaloideus), located between an optic disk and a crystalline lens. By 6th month of pre-natal development the secondary vitreous is formed of a mesoderm and an ectoderm, its fibrous skeleton begins to form. S.'s vessels of t. gradually zapustevat. By the time of the birth the artery of a vitreous, kloket disappears the channel usually remains, but quite often is absent or does not reach a crystalline lens. Newborn S. has a t. it is finally created (tertiary S. of t.).

Anatomy

S. of t. conditionally divide into 3 parts: zakhrustalikovy (pars retrolentalis), separated from crystalline lens (see) slit-like zakhrustalikovy space and having deepening on the front surface — a vitreous pole (fossa hyaloidea); ciliary (pars cillaris) adjacent to a flat part ciliary body (see), and back (pars posterior), adjoining to to a retina (see).

Kloketov the channel is located in S. with t. between an optic disk and a crystalline lens in the form of a narrow S-shaped tube. On S.'s surface of t. there is a thin cover — a boundary membrane, or a vitreous table (a vitreous membrane, T.; membrana vitrea), adjoining directly on an inner boundary membrane of a retina. Page of t. it is attached to surrounding fabrics in several places: ring-shaped zones of an attachment are located along a flat part of a ciliary body and a back surface of fibers of a tsinnovy sheaf (a ciliary corbel, T.; zonula ciliaris), in the field of a back surface of the capsule of a crystalline lens (is closer to its equator) — lig. hyaloideocapsulare, on a circle of an optic disk and a macula lutea of a retina; to S.'s retina of t. it is attached in places of passing of its vessels, in the areas corresponding to an equator of eyeball and places of an attachment of outside muscles of an eyeglobe. Vessels and S.'s nerves of t. has no.

Histology

the Diagrammatic representation of structure of a vitreous according to G. Eisner on a sagittal section of an eyeglobe (the vitreous is designated in gray color): 1 — a cornea; 2 — a sclera; 3 — an optic nerve; 4 — a crystalline lens; 5 — kloket the channel; 6 — a hyaloid path; 7 — a coronal path; 8 — a median path; 9 — a preretinalny path.

Page of t. consists of the fibrous skeleton and friable substance filling intervals between fibers. Eisner (G. Eisner, 1975) considers that fibers C. of t. are located in the form of so-called vitrealny paths — preretinalny, median, coronal and hyaloid, forming bedded structure of a vitreous (fig). At S.'s studying t. by means of phase and contrast, polarizing and a submicroscopy in it fibers of three types were found: fibers of the glial nature, prekollagenovy fibers and fibers from gel. In interfibrillar substance of a peripheral layer of S. of t. (is closer to the equator) find own cells of S. of t. — gialotsita, occasionally aletocytes.

Biochemistry

In the biochemical relation of S. of t. represents the hydrophilic gel containing 98 — 99% of water. A consistence of gel in the central part C. of t. more liquid in comparison with the condensed peripheral departments. Protein in S. of t. is available in a small amount, the prevailing part it is made by albumine. Specific protein C. of t. is vitrozin — the sticky, water-insoluble hydrophilic substance forming one of types of fibers C. of t. Interfibrillar space of S. of t. fills difficult mukoproteid, to-rogo is a part hyaluronic to - that (see. Hyaluronic acids ). Constant volume and S.'s turgor of t. it is provided generally with ability hyaluronic to - you to hold a large amount of water. At the same time only apprx. 10% of water C. of t. is in chemically connected state that supports its high water exchange. With immunol. points of view of S. of t. represents special fabric, free of antibodies and gamma-globulin.

Functional value

S. of t., filling a cavity of an eyeglobe, except for front and back chambers of the eye, promotes preservation of a form of an eyeglobe and, putting pressure upon the covers surrounding it (first of all, upon a retina), supports them in a certain situation. Besides, S. of t. is a part of the refracting system of an eye (see. Refraction of an eye ).

Methods of a research

Klin, research C. of t. carry out by means of a transmitted light and biomicroscopy. Normal at a research in a transmitted light (see. Inspection of the patient, ophthalmologic ) Page of t. optically it is transparent, its structure does not come to light; at patol. processes in S. of t. this method allows to find floating or diffusion opacities. The fullest idea of S.'s structure of t. it is possible to receive at biomicroscopy (see Biomicroscopy of an eye) using the lenses neutralizing optical system of an eye. For a research C. of t. apply also one - or a two-chamber ekhografiya (see. Ultrasonic diagnosis, in ophthalmology ).

Pathology

S.'s Pathology of t. includes malformations, damages and diseases.

Malformations. To inborn malformations of S. of t. the remains of an embryonal artery of a vitreous (a. hyaloidea persistens) belong. Sometimes the remains of this artery have an appearance of the tyazh going from an optic disk to a crystalline lens on the course of a kloketov of the channel, in nek-ry cases only the part of the obliterated artery connected with an optic disk or with a back pole of the lens remains. These anomalies, as a rule, do not break visual functions, come to light accidentally at biomicroscopy of an eye and treatment do not demand.

Damages. S.'s loss t. perhaps at perforated wounds of an eye, and also during the operations which are followed by opening of an eyeglobe. At the same time there is a loss of substance C. of t., the shift and a tension of vitrealny paths towards a wound opening. In case of loss no more than 1/3 mass of S. of t. there is its substitution intraocular liquid. At loss of bigger mass of S. of t., usually coming to an end atrophy of an eyeglobe, showed substitution of the dropped-out part C. of t. physiological solution of sodium chloride, silicone.

At dislocation and an incomplete dislocation of a crystalline lens (is more often than a traumatic origin), and also after intrakapsulyarny extraction of a cataract in pupillary area herniation of S. of t is possible., can lead edges at contact with a back epithelium of a cornea to development of violent dystrophy of a cornea — a violent edematous keratopathy (see. Cornea ). As a rule, S.'s hernia of t. does not break visual functions and does not demand treatment. At the hernia contacting to a back epithelium of a cornea the vitreoektomiya is recommended.

In S. of t. various foreign bodys can get.

In the presence in an eyeglobe of foreign bodys diffusion opacifications of S. of t can be observed., leading to disturbance of visual functions (see. Foreign bodys, eyes).

Diseases. To patol. to S.'s changes t. refer destruction, pathological inclusions in its substance (exudate, blood, products of exchange, parasites). These changes arise, as a rule, for the second time at an inflammation of a choroid of an eyeglobe (see. Iridocyclitis , Uveitis , Choroiditis ) or retinas, retinopathies (see), short-sightedness (see), injuries of an eyeglobe (see. Eye, damages ), the general diseases of an organism — a diabetes mellitus (see. diabetes mellitus ), atherosclerosis (see) and others patol. processes. A wedge, symptomatology at patol. S.'s changes t. it is caused by hl. obr. disturbance of its transparency as optical environment, and also change of topography and S.'s volume of t.

Destruction Page of t. in the form of its fluidifying (transition of gel to sol) and opacification it is observed at short-sightedness of high degree, at elderly people, at a diabetes mellitus, etc. At S.'s fluidifying t. patients, as a rule, do not show complaints. At a biomikroskoiiya a zone of fluidifying of S. of t. more mobile looks, floating particles of a fibrillar skeleton are visible. Further in the liquefied part C. of t. colloid micelles in the form of lumps of various size and a form, and S. of t drop out. grows turbid. At S.'s opacification t. easy degree the patient has feelings of «the flying front sights» (see. flying ). At more considerable opacification the patient has subjective feelings of floating strips, tapes, etc. At a research in a transmitted light and biomicroscopy of an eye (see) opacifications have an appearance of threads, flakes, translucent films, to-rye are displaced at the movements of an eyeglobe.

Heavy destructive changes of S. of t. (education connective tissue tyazhy, shvart) are noted at newborns at retrolental fibroplasia (see).

Rather often destructive processes in S. of t., developing at short-sightedness of high degree and at persons 50 years are more senior, lead to back ring-shaped amotio of S. of t. (S.'s separation of t. from an optic disk), sometimes from simultaneous amotio of a retina (see). Development of amotio of S. of t. is followed photopsia (see) that is connected with a tension of a retina. After the termination of amotio of the patient notes emergence before an eye of «opacification» in the form of a ring, a horseshoe, etc. At biomicroscopy of an eye reveal the gray oval ring located ahead of an optic disk and the subvitrealny space filled with liquid.

Destructive processes in S. of t. proceed slowly. Apply instillation of solutions of potassium iodide, an ionophoresis with lidazy (hyaluronidase), streptolidazy (Streptokinasa) to a rassasyvaniye of opacifications, etc., and also osmotherapy and fabric therapy (see). In the absence of effect appoint intravit-real administration of proteolytic enzymes. Treatment of amotio of S. of t. inefficiently.

S.'s opacification t. it can be caused by penetration in it of the exudate consisting of cellular elements and fibrin that is observed at inflammatory diseases of a vascular path (an iridocyclitis, twine, a choroiditis) or retinas (retinitis). Depending on character of an iridocyclitis, a uveitis, a choroiditis or a retinitis exudate in S. of t. can be serous, hemorrhagic or purulent. At acute purulent twine t in S. the suppurative focus (abscess) can be formed or develop diffusion suppuration of S. of t.

Treatment is directed to a basic disease and a rassasyvaniye of opacifications of S. of t. At abscess and diffusion suppuration of S. of t. intravitrealno enter antibiotics (penicillin, gentamycin, etc.). Result of inflammatory opacifications of S. of t. it is various. In some cases exudate can resolve in whole or in part, at heavy and is long the proceeding inflammatory processes in a choroid of an eye or in a retina S.'s chemism of t changes., connecting unions form that leads to considerable decrease in visual functions. Diffusion suppuration of S. of t. often comes to an end with death of an eye (see Panoftaljmit, Endoftaljmit).

Hemorrhages in S. of t. (from vessels of a retina or a choroid of an eyeglobe) can arise at wounds and contusions of an eyeglobe, cardiovascular diseases, a diabetes mellitus, etc. At young age the so-called recuring juvenile hemorrhages in S. are observed by t., to-rykh the periphlebitis of a retina or, more rare, vasculites of various etiology is the main reason. Blood impregnates S. with t. partially or completely (see. Hemophthalmia ).

Sometimes in S. of t. at biomicroscopy of an eye find crystals of cholesterol, tyrosine, etc., floating at the movement of an eyeglobe as a rain from golden or silvery spangles — so-called blinking of S. of t. (synchisis scintillans). Emergence of crystals in some cases is a consequence of hemorrhages in S. of t. or exchange disturbances. Visual functions, as a rule, are not broken.

In S. of t. can get parasites, getting there generally from subretinal space. Find a cysticercus more often, filarias, an echinococcus, etc. are more rare. Parasites are deleted in the operational way through a section in covers of an eyeglobe (see. Eye , Filariases , Cysticercosis , Echinococcosis ).

At heavy patol. processes in S. of t., the visual functions which are followed by falloff and not giving in to conservative treatment an operative measure is shown. At the end of 19 century applied suction patholologically of the changed S. of t. the special needle offered Ned-denom (M. W. Nedden). In the subsequent the taken S. of t. began to replace with physiological solution of sodium chloride, silicone and other transparent substances. In recent years the equipment allowing to carry out a vitreoektomiya is developed (fragmentation, aspiration and S.'s substitution of t.) at a fixed level of intraocular pressure, but in connection with injury of operation and need for its carrying out the difficult equipment it was not widely adopted.

Vitreous as drug

S. of t. is biologically active fabric drug, to-ry receive t from S. lethal cattle.

Page of t. — colourless, transparent, inodorous slightly opalescent liquid and taste; represents a complex colloid system, a cut water, collagen, proteins of serum, hyaluronic and ascorbic to - you, a number of salts and metabolites are a part.

Pharmakol. S.'s effects of t. connect with effect of the hyaluronic acid which is contained in it (see. Hyaluronic acids ). Page of t. is a biogenic stimulator (see), reduces fabric permeability, promotes a softening and a rassasyvaniye of cicatricial fabric, possesses the anesthetizing action, stimulates formation of a bone callosity at changes.

Page of t. apply for treatment of keloid, extensive postoperative cicatrixes, at contractures of joints, changes; as anesthetic C. of t. appoint at an epileptiform neuralgia, radiculitis, stump neuralgias. Page of t. apply also in dermatology to treatment of a scleroderma. In ophthalmologic practice of S. of t. use for treatment of an atrophy of an optic nerve, malignant short-sightedness, a pigmental retinitis, a neuroretinitis, an iritis, a uveitis, a keratitis, ulcers and burns of a cornea, cicatricial changes a century.

Page of t. enter subcutaneously 2 ml of 1 times a day during 1 — 3 week. At a scleroderma — directly in the center of defeat. There are data on efficiency of podkonjyunk-tivalny injections of S. of t. (on 0,3 — 0,5 ml) at a keratitis, ulcers and burns of a cornea.

Page of t. contraindicated at inf. diseases, exhaustion, diseases of parenchymatous bodies, heart failure, oncological diseases.

Page of t. not toxically, usually does not cause by-effects. Allergic reactions to S.'s introduction of t are possible.

Form of release: ampoules on 2 ml. Store S. of t. at the room temperature in the dry and dark place.



Bibliography: Krasnov M. M. Microsurgery of an eye and intraocular implants, in book: Aktualn. probl. Ophthalmolum., under the editorship of M. M. Krasnov, etc., page 7, M., 1981; The Multivolume guide to eye diseases, under the editorship of V. N. Arkhangelsky, t. 2, book 2, page 523, M., 1960; About l I to B. L. Field ophthalmology, JI., 1957; The Vitreous in clinical ophthalmology, under the editorship of. A. I. Gorban, etc., century 2, D., 1979; E i s-n e r G. Zur Anatomie des Glaskorpers, Albrecht v. Graefes Arch. klin. Ophthal., Bd 193, S. 33, 1975; Lehrbuch und Atlas der Augenheilkunde, hrsg. v. H. Pau, Stuttgart, 1973; Machemer R. A a b e r g T h. M. Vitrectomy, N. Y., 1979.


G. M. Laryukhina; D.N. Samoylov (pharm.).

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