CHOROID OF A EYE

From Big Medical Encyclopedia

CHOROID OF A EYE [tunica vasculosa bulbi (PNA), tunica media oculi (JNA), tunica vasculosa oculi (BNA); synonym: vascular path of an eye, uvea] — the average cover of an eyeglobe rich with vessels and located between a sclera and a retina.

In a choroid of an eye (an eyeglobe, T.) distinguish the front department presented by an iris (see) and a ciliary body (see) and back — an idiovascular cover of an eye, or horioideyu [choroidea (PNA), chorioidea (BNA)], the borrowing most part of S. of the lake of. Actually S. of the lake of forkhmirutsya on the 5th month of pre-natal development from a powerful shoot of a mesoderm * the eyecup getting into a cavity on site of transition of a leg of an eyecup to it.

The anatomy

Actually S. of the lake of extends from gear edge (ora serrata) to an optic nerve (see). Outside it borders on a sclera (see), separating from it a narrow crack — perikhorioidalny space (okolososudisty space, T.; spatium perichoroide-ale), a cut is finally formed only to the second half of the year of life of the child. It is densely connected to a sclera only in the field of an exit of an optic nerve. From within to actually S. the lake of is closely prilezhit by a retina (see). Thickness actually of S. of the lake of fluctuates depending on a krovenapolneniye from 0,1 to 0,4 mm.

The vascular system actually of S. of the lake of is presented by 8 — 12 back short ciliary arteries (aa. ciliares breves), to-rye are branches of an eye artery (a. ophthalmica) and lakes of at a back pole of the eyeball, forming dense vascular network get into actually S. A venous blood from S. of the lake of flows on vortikozny veins (vv. vorticosae), which via slanting channels in a sclera 4 — 6 trunks leave an eyeglobe.

S. of the lake of long and short ciliary nerves innervate (nn. ciliares longi et breves).

Histology

Diagrammatic representation of a histologic structure of an idiovascular cover of an eye (cross section): I \suprakhorioidalny plate; II \layer of large vessels (Galler's layer); III \layer of average vessels (Zattler's layer); IV \choriocapillary layer; V \vitreous table (Bruch's membrane); 1 — a pigmental epithelium of a retina; 2 — pigment cells; 3 — arteries; 4 — veins; 5 — a sclera.

In actually S. islands of distinguish 5 layers (fig.): 1) a supra-choroidal plate — the periblast adjoining a sclera, consisting of the thin connective tissue plates located in 5 — 7 rows and covered with mnogootrostchaty pigment cells (see); 2) the layer of large vessels (Galler's layer) consisting from quite large, preferential venous vessels, intervals between to-rymi are filled with friable connecting fabric and pigment cells; in this layer vortikozny veins originate; 3) the layer of average vessels (Zattler's layer) consisting preferential of arterial vessels and containing less than pigment cells than Galler's layer; 4) a choriocapillary layer (a horoidalno-capillary plate, lamina choroidocapillaris) having a peculiar structure (capillaries lacunas are located in one plane and differ in the unusual width of a gleam and narrowness of intercapillary intervals), thanks to what almost continuous circulatory collector separated from a retina only by a vitreous table is created; the network of vessels in a choriocapillary layer at a back pole of the eyeball in the field of the central pole of the retina providing functions of the central and color sight is especially dense; 5) vitreous table, or Bruch's membrane (basal complex, or basal plate, T.), the 2 — 3 microns thick, separating choroid from a pigmental epithelium of a retina.

Perivascular spaces actually of S. of the lake of are occupied by the stroma consisting of friable connecting fabric (see). Except fibrocytes and the wandering histiocytes actually of S. the lake of contains pigment cells, bodies and numerous shoots to-rykh are filled with fine grains of a brown pigment. They give actually S. the lake of dark coloring.

The physiology

Actually S. of the lake of provides food and normal functioning of a retina: the choriocapillary layer supplies with blood periblasts of a retina, including a bacillary layer where there is a recovery of continuously breaking up rhodopsin (rhodopsin) necessary for sight (see). Besides, actually S. of the lake of, thanks to existence in it of hemoten-zoretseptor, participates in regulation of intraocular tension.

Methods of a research

Methods of a research include an oftalmoskopiya (see), the oftalmokhro-Moscow copy, a diafanoskopiya (see), a fluorescent angiography (see), ultrasonic biometrics (see. Ultrasonic diagnosis). Actually of S. lakes of apply radio-isotope researches with radioactive phosphorus 32P, iodine 1311, krypton 85 of Kg to diagnosis of new growths.

For the purpose of specification of the diagnosis widely use immunological methods of a research (see the Immunodiagnosis). Serological researches concern to them: agglutination tests (see), precipitations (see), microprecipitations across Uanye (a method of a nefelometriya), reaction of binding complement (see); quantitative definition of immunoglobulins in biol. liquids (blood serum, the lacrimal liquid, watery moisture of an anterior chamber of an eye, etc.) Mancini's method. Apply reactions of a blastotransformation of lymphocytes to a research of cellular immunity (see), braking of migration of leukocytes, a leykotsitoliza. For specification of an etiology of inflammatory diseases (choroidites, uveites) carry out also focal tests with use of offending allergens (tuberculine, a toksoplazmin, the cleared bacterial and viral antigens, fabric antigens C. of the lake of). Allergen is applied on skin or entered vnutrikozhno, subcutaneously or by an electrophoresis then watch a current of a choroiditis (or a uveitis). Test is considered positive at emergence of an aggravation of a choroiditis (uveitis) or at reduction of an inflammation.

Pathology

Distinguish malformations, damages, diseases, S.'s tumors of the lake of.

Malformations. The most frequent anomaly of development actually by S. of the lake of is the coloboma (see). Sometimes S.'s underdevelopment of the lake of - — a horioderemiya, a nevus pigmentosus of S. of the lake of meets, to-rye do not demand special treatment.

Damages are observed at the getting wounds, contusions, operative measures (see an Eye, damages).

Amotio actually of S. of the lake of can arise at injuries of an eye, and also after band operations on an eyeglobe (antiglau-coma, extractions of a cataract, etc.). At the same time in perikhorioidal-number space transudate, S. otslaivayushchy actually of the lake from a sclera accumulates. Amotio actually of S. of the lake of can be also result of disturbance of a shelter

of the address in it at falloff of intraocular pressure.

A wedge, signs of amotio actually of S. of the lake of are decrease in visual functions, a small and uneven anterior chamber of an eyeglobe, decrease in intraocular pressure. At an oftalmoskopiya it is visible gray bubble color of S. otsloyenny actually of the lake of. The diagnosis is made on the basis by a wedge, pictures, data of perimetry, ultrasonic investigation (see. Ultrasonic diagnosis, in ophthalmology) and diafanoskopiya (see). Treatment conservative: subconjunctival injections of caffeine, Dexasonum, inside digoxin, veroshpiron, Ascorutinum. In the absence of effect operational treatment is shown: back trepanation of a sclera (see) or a sclerotomy (see the Sclera) for removal of excess perikhorioidalny liquid. The forecast at timely treatment favorable.

Diseases. Inflammatory processes can develop in all departments of a choroid (see the Uveitis) or only in its back department — a back uveitis, or a choroiditis (see).

Features of a structure and function C. of the lake of define an originality of inflammatory processes. The abundance of vessels, an anastomosis between them, a wide gleam of capillaries cause delay of a blood-groove and create favorable conditions for sedimentation in S. to the lake of of bacteria, toxins, viruses, the elementary and others patol. agents. A large number of pigment cells, histiocytes, existence of proteins, mucopolysaccharides (glikozaminoglikan) causes a high antigenic organospetsifichnost actually of S. of the lake of and creates premises for development of an allergy at inf. defeats. The immune conflict can be shown by allergic reactions of the slowed-down type (more often) and immediate type.

Tumors. From benign tumors neurinoma (see), angiomas, iyevusa meet (see Neva with, eyes). Neurinoma of a choroid usually develop against the background of a neurofibromatosis (see). S.'s angiomas of the lake of are observed seldom, regard them as a malformation of vascular system of an eye. As a rule, they are combined with similar anomalies of face skin and mucous membranes.

Actually of S. lakes of subdivide malignant tumors on primary and secondary. Primary tumors develop from elements actually of S. of the lake of, secondary — at innidiation from primary center located in a mammary gland, lungs went. - kish. path.

The most widespread malignant tumor actually of S. of the lake of is the melanoma (see). Apply a lazerkoagulyation to treatment of malignant tumors (see the Laser), a resection of a tumor, the cryodestroying operations (see the Cryosurgery), according to indications — radiation therapy, chemotherapy, sometimes resort to removal of an eyeglobe (see Enucleation of an eye).

Actually of S. lakes of in combination with cryoinfluence make excision of peripheral departments during removal of tumors. Actually of S. lakes of carry out a section for introduction to a cavity of an eye of various tools during removal of foreign bodys (see), operations on a vitreous (see), a retina (see).

See also Eye .



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O. B. Chentsova.

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