ELEKTRORETINOGRAFIYA

From Big Medical Encyclopedia

ELEKTRORETINOGRAFIYA [electro-(from «electricity») + late lat. retina a mesh cover + grapho to write, represent] — a method of a research of a functional condition of a retina of an eye by registration of biopotentials (action currents) arising in it at photoirritation.

Elektroretinografiya is carried to number of objective methods elektrofiziol. diagnoses of defeats of the visual and nervous device of an eye (see the Electrophysiology of an organ of sight). The greatest value E. has in diagnosis of nek-ry types of hereditary diseases of peripheral department of a retina, e.g. tapetoretinalny abiotrofiya (see Tapetoretinalny dystrophies), for identification of early changes of a retina at a diabetes mellitus (see Retinopathies), a siderosis of an eye (see), and also during the forecasting of a result of surgeries at patients with opaque optical environments of an eye, e.g. at a cataract (see), an opacity of the vitreous body (see), etc.

At E. carry out stimulation of an eye pulse light sources. For impulses of this world special fotostimulya-Torahs, for impulses of monochromatic radiation — quantum generators serve (see the Laser). For the purpose of registration of biopotentials usually use electroencephalographs (see Elektroentsefalografiya). Active electrodes can be ocular and extraocular. Ocular electrodes in the form of contact lenses with the silver or platinum contacts which are built in in them after preliminary anesthesia establish on a cornea, extraocular electrodes in the form of hooks and plates fix on a lower eyelid. The passive electrode (clip) is usually fixed to a lobe of an ear.

After dark adaptation within 3 — 5 min. and installation of electrodes influence the studied eye single light pulses or their series and register the arising biopotentials of a retina in the form of a curve — electroretinograms.

The normal electroretinogram consists of electropositive and electronegative rejections, or waves (fig). Waves of the electroretinogram, according to the most recognized concept (1933), represent registration of one or several potentials caused by cells of different layers of a retina — the summary electroretinogram. Most of researchers connect an origin of these biopotentials with processes and formation of nervous excitement photo chemical in periblasts of a retina. Usually consider the so-called simplified electroretinogram, estimating their amplitude and frequency (the reproduced rhythm of photoirritations. At the same time consider that the wave of a generally characterizes a functional condition of coneal system of a retina (the photopic electroretinogram), and a wave of b — bacillary system (a scotopic retinogramma). The average value of amplitude of a wave of a normal makes 50 mkv, waves of b — to 400 mkv. The origin and the characteristic of late electropositive waves of c and d are insufficiently studied.

Fig. The electroretinogram which is written down from a surface of a cornea of the person: and - electronegative waves; b - electropositive waves; c, d — entrance electropositive waves; on ordinate axis amplitude of a wave is designated (in microvolts), on abscissa axis — time in milliseconds); vertical dashed lines limited duration of a light pulse.

At high intensity of a light incentive (St. 100 J) it is possible to reveal additional waves of a retnnogramma — its so-called sluggish components, the origin is connected only with a photo processes in outside segments of photoreceptors, and also by the components characterizing generally photopic processes of a retina of an eye.

Depending on character patol. process in a retina distinguish several types of the electroretinogram differing with amplitude and the direction of waves. At focal processes in periblasts of a retina, at patients with a retinopathy, amotio of a retina (see), observe decrease in amplitude of waves and (from 25 to 10 mkv) and b (from 150 to 75 mkv) — the so-called subnormal electroretinogram. More expressed decrease in height of waves the so-called disappearing electroretinogram) can be observed at patients with a tapetoretinalny abiotrophy. At disturbances of blood supply of a retina increase in amplitude of a wave can be observed and (the negative electroretinogram).

In recent years attempts of registration of the local electroretinogram by use as a light irritant of monochromatic radiation are made that allows to estimate a functional condition of macular area of a retina.

Bibliography: Granite P. An electrophysiologic research of reception, the lane with English, page 151, M., 1957; Ophthalmologic electrodiagnosis, under the editorship of K. V. Trutneva, M., 1980; Newell F. W. Ophthalmology principles and concepts, p. 88, St Louie, 1982; Peregrin J. u. Sverak J. Elektroretinographia und Elektrookulographia, Hradci Kralove, 1977.

G. M. Laryukhina.

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