TONOGRAFIYA

From Big Medical Encyclopedia

TONOGRAFYYa (Greek tonos tension of Hr grapho to write, represent) — a quantitative research of balance of products and outflow of intraocular liquid.

T. has important theoretical and clinical value since is the only method providing a possibility of intravital studying of hydrodynamics of an eye (see). Value T is especially big. at glaucoma (see), as disturbance of outflow of intraocular liquid (as the result of it increases intraocular pressure) — one of the main and initial displays of a disease. At the same time practical value T. (first of all as method of early diagnosis of glaucoma) it was exaggerated earlier.

Development and deployment of T. in a wedge, practice in 50 — the 60th 20 century are connected with Moses and Bruno's works (V. Moses, M. Bruno, 1950), Becker, Schaffer (V. Becker, R. Shaffer, 1961), M. M. Krasnova (1963), A. II. Nesterova (1967), etc.

T. the compress of the ion-tonometric research based on the dosed pressure (a compression of an eye), naira, by a tonometer weighing 15 or 17,5 g within several minutes is one of types. Such compression of an eye causes immediate increase in intraocular pressure. As a result of it compensatory outflow of intraocular liquid from a cavity of an eye with gradual decrease in intraocular pressure begins that partially levels its initial rise. In size of this compensatory decrease in intraocular pressure judge ability of intraocular liquid to outflow and a condition of outflow tracts.

For carrying out T. produce surface anesthesia of a cornea and conjunctiva, just as at a tonometriya (see). A contraindication to T. usually are patol. processes in a cornea and a conjunctiva (especially inf. character).

The most important indicator of T. the coefficient of ease of outflow — is With, to-ry normal makes 0,15 — 0,55 mkl/mm of mercury. in 1 min. It is calculated on a formula:

with =-_

(r sr_ ro __!? 2 5 j - t’ where A V — the total quantity of intraocular liquid which left a cavity of an eye as a result of its compensatory outflow (it is calculated on a difference between sizes of intraocular pressure to and

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after a compression); R — an arithmetic average of results of a tonometriya (in mm of mercury.) before and after a compression of an eye; P0 — «true» intraocular pressure; t — vrvkhmya (in min.), during to-rogo is made pressure approximately; 1,25 — allowance for build-up of pressure in episkleralny veins, in to-rye is flowed by intraocular liquid.

About products of intraocular liquid judge by so-called minute volume — F, to-ry, according to most of researchers, makes normal 1,5 — 2,0 mkl! min. This indicator is calculated on a formula: F ~ With (Po-Pyh where With — coefficient of ease of outflow; P0 — «true» intraocular pressure; Pv — pressure in episkleralny veins, in to-rye is flowed by intraocular liquid (is accepted ravnsh 10 mm of mercury.). The given calculations assume a number of assumptions: it is postulated that the level

of products of intraocular liquid during the research does not change, the amount of blood in a choroid of an eye remains to constants, the level of outflow of intraocular liquid is proportional to increase in intraocular pressure as a result of a compression, etc.

On the basis of a number of the researches conducted in recent years it is established that these assumptions are not proved, and topographical calculations considerably simplify and schematize the true changes occurring at T. Besides, pressure of a tonometer upon a cornea, by data And. II. Nesterova, can negatively influence outflow of intraocular liquid since fabric of a cornea on the periphery of a zone of a compression is pushed aside to ways of filtering of liquid from an eye and can partially block them. The method konveks - nografni allows to avoid it, at Krom pressure on ro-

to goviyets is carried out by a convex surface of a tonometer thanks to what in a circle of a zone of contact between a tonometer p the shift of fabrics does not occur a cornea.

At T. by the simplified method the research is made a tonometer weighing 15 g of Maklakov (see Tonometers). The compression of an eyeglobe is carried out by the same tonometer within 4 min. On change of intraocular pressure after a compression in comparison with initial judge ability of intraocular liquid to outflow. In a crust, time for carrying out T. most often use an electronic tonometer (usually to them and a yard-sionny), the sensor to-rogo allows to transform the size of intraocular pressure to electric potentials of a certain size. The result of a research is registered graphically by means of the recorder.

Bibliography: Krasnov M. M. Microsurgery of glaucomas, M., 1980; Neste

A. P. Gidrodinamik's ditch of an eye, M., 1968; it, Primary glaucoma, M., 1982; Adler F. N of Adler's physiology of the eye, clinical application, St Louis, 1975; I w a t a K. Clinical estimation of aqueous outflow through trabecula and outlets of Schlemm’s canal, in book: Recent ad-vanc. in glaucoma, ed. by S. Rehak a. o., p. 39, V. a. o., 1977. M. M. Krasnov.

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