GONIOSKOPIYA (Greek gonia a corner + skopeo to observe, investigate) — a method of visual examination of an angle of iris of an anterior chamber of an eye.
Angle of iris (a corner of an anterior chamber of an eye — tsvetn. fig. 1) is not visible at simple survey through a cornea because the beams going from here towards an eye of the observer undergo total internal reflection on border between a cornea and air owing to a big difference in indices of refraction of these two environments in combination with a slanting path of rays. Thus, the border a cornea — air plays a role of the mirror reflecting the image of a corner in an eyeglobe here. In this regard special methods are developed for observation of a corner of an anterior chamber.
Early studies of this area were conducted in 1898 by A. Trantas, later the term «gonioskopiya» was offered them.
One of the main indications to G.'s carrying out is glaucoma (see). The research can be made for the purpose of diagnosis of glaucoma, carrying out the differential diagnosis between primary and secondary glaucoma, and also in the preoperative period since the form of an angle of iris and a condition of the filtrational device shall be considered at the choice of antiglaukomatozny operation. A number of antiglaukomatozny operative measures became possible only with the advent of G. (see. Goniotomy, goniopuncture ). G.'s carrying out later a nek-swarm time after fistuliziruyushchy operations for definition of a condition of outflow tracts of intraocular liquid is reasonable.
It is obligatory at the tumors located in the field of a root of an iris. It allows to define borders of a tumor that quite often causes a question of a possibility of its removal and preservation of an eyeglobe.
It is shown at the foreign bodys in an angle of iris which are especially not revealed at rentgenol, a research (glass, aluminum).
Zaltsmann (M. of Salzmann, 1914, 1915) suggested to use the special contact glasses adjacent to an eyeglobe for G. The design of these glasses allows to avoid the phenomena of total internal reflection. Later gonioscopy lenses, more perfect types of contact lenses were developed for G. (fig. 1). The main lack of gonioscopy lenses — need of use of contact solution for filling of space between a lens and an eye, and also practical inevitability of a research of the patient in a prone position and from the different parties that creates considerable inconveniences for use of the strong increasing systems.
In 1938 Mr. H. Goldmann offered the device for G., use to-rogo led to improvement of a technique of a research. In the cylinder from organic glass, one of the ends to-rogo is constructed as a gonioscopy lens, the small pocket mirror (fig. 2) reflecting a picture of any site of an angle of iris towards eyes of the observer who is face to face with the patient is included. At each separate moment the site of a corner located against a mirror is visible (apprx. 1/3 all circles); for survey of a corner throughout the device it is necessary to turn around its longitudinal axis. Allowed to work this invention for the purposes G. usual slit lamps (see) and to make a research at position of the patient sitting.
In 40 — the 50th 20 century some other the designs which are characterized by a similar path of rays was developed. All these devices carry the name of «gonioskop» (fig. 3 and 4). In Ophthalmolum. to clinic Goldmann, Allen and O'Brien (1945), Allen's gonioskopa — Braly — Thorp, Van-Boyningena (1953), M. M. Krasnov (1956) are applied, G. S. Zarubina (1960), etc.
Technique of a research
Before G. enter solution of any anesthetizing substance into a conjunctival sac of an eye of the patient (e.g., 0,5 — 1% of solution of Dicainum). Gonioskop enter for eyelids of the studied eye and press to a cornea. The picture of a corner of an anterior chamber seen through gonioskop is considered in a microscope of a slit lamp at necessary (most often 20-fold) increase and during the use of an optical cut (see. Biomicroscopy of an eye ).
Structures (zone) of an angle of iris. A front surface of a ciliary (tsiliarny) body — a grayish-brown strip, usually with not absolutely equal, wavy borders. A scleral spur — the place of an attachment of a ciliary body to a sclera — narrow, usually yellow-white strip. This zone is designated also as a back boundary ring of Shvalbe. 3ona corneoscleral trabeculas — rather wide strip with equal borders, usually pale gray color which is often semi-translucent. In this area this or that extent of pigmentation is quite often noted. A zone of a venous sine of a sclera (a shlemmov of the channel) — the narrow strip passing in limits of a zone of a corneoscleral cover, approximately on its middle, and differing in more dark coloring. Often the channel is not visible. At some patol, states, and also is normal, after massage of an eyeglobe, it is filled with blood. Sometimes, especially at advanced age, the area of a shlemmov of the channel is pigmented. Cutting — the narrow groove delimiting a zone of a corneoscleral cover from the following area — a so-called front boundary ring of Shvalbe. A front boundary Ring of Shvalbe — usually well reflexing white strip between a zone of corneoscleral trabeculas and the field of occurrence in an eyeglobe of the pro-butting branches of front tsiliarny vessels that approximately corresponds to position of area of a limb. A cornea — the dome-shaped light zone delimiting everything the areas noted above from outside, an iris of the eye opposite to a root. Often at G. are visible also edge sheaf (in the form of the fibers reaching from a root of an iris for area of a corneoscleral cover) and border of a back boundary plate (a descemete cover) — the narrow white line around a front boundary ring of Shvalbe.
At G.'s carrying out the form of an angle of iris is defined. Depending on extent of closing with an iris of identification zones of a corner distinguish wide, average width, the narrow and closed corner. At wide coal all identification zones are well visible. The strip of a ciliary body is represented wide. The wide corner is observed at a myopia (see. Short-sightedness ) and aphakias (see). Most often the corner meets average width. It is characterized by the fact that at it the root of an iris almost completely or completely covers a strip of a ciliary body.
At narrow coal it is possible to see identification zones only to a scleral spur. The strip of a ciliary body and a scleral spur are covered with a root of an iris. Sometimes happens partially covered and a zone of corneoscleral trabeculas that prevents to see helmets the channel. The narrow corner is most often observed at a hypermetropia (see Far-sightedness). If the iris covers all zones of an angle of iris, say about the closed coal of an anterior chamber that it, as a rule, takes place only at patol, states — at a bad attack of glaucoma, in case of blockade of zones of a corner a tumor of an iris, etc.
Goniotsikloskopiya — method, essentially similar to G. Goniotsikloskopiya allows to explore the area of a flat part of a ciliary body and the peripheral departments of a retina not available to an oftalmoskopichesky research. Carrying out it happens perhaps at the most mydriatic pupil and at a transparent crystalline lens or its absence (aphakia).
Contraindications to G. — any conjunctivitis, dacryocystites, a keratitis and helcomas.
Bibliography Krasnov M. M. Microsurgery of glaucomas, M., 1974, bibliogr.; Pole B. L. and M. B. O of a gonioskopiya is sensitive at glaucoma and at foreign bodys in a corner of an anterior chamber, Vestn, oftalm., No. 2, page 26, 1950; The Guide to eye surgery, under the editorship of M. L. Krasnov, M., 1976, bibliogr.; Shulpina N. B. Biomicroscopy of an eye, M., 1974, bibliogr.; Becker B. Diagnosis and therapy of the glaucomas, St Louis, 1970; Frangois J. La gonioscopie, Louvain, 1948; Salzmann M. Die Ophthalmo-skopie der Kammerbucht, Z. Augenheilk., Bd 31, S. 1, 1914, Bd 34, S. 26, 1915; System of ophthalmology, ed. by S. Duke-Elder, v. 11, L., 1969.
M. M. Krasnov.