From Big Medical Encyclopedia

DIPLOPIA (grech, dipl[oos] double + ops, opos of eyes) — doubling of the image of the considered subject as a result of a deviation of a visual axis of one of eyes. Is observed at damage of the nerves innervating oculomotor muscles (see. Block nerve , Third cranial nerve , the Taking-away nerve ).

Scheme of the mechanism of a diplopia: and p and and l — central poles of a retina of the right and left eye; About — a point of fixing of a look; ah — the site of a retina of the left (rejected) eye on which the point is projected About; O 1 — a virtual image of a point Oh, seen by the left eye.

Kernels of these nerves are located in a brainstem. The easing of sokratitelny ability of muscles which occurred in connection with disturbance of an innervation leads to a deviation of an eye aside. Can be observed also at various patol, processes in bone walls and in a cavity of an eye-socket, leading to the considerable shift of an eyeglobe, at damages and cicatricial changes of muscles of an eye. At the Diplopia the image of the considered subject gets in correctly fixing eye on the central pole of a retina, and in rejected — on the noncentral site of a retina. The visual object of the rejected eye on association with the usual space relations is projected to that place of space where there would have to be a subject to cause irritation of this site of a retina (fig.) at the correct provision of a visual axis of this eye. Distinguish D. of the same name at which the second (imaginary) image is projected towards the rejected eye, and a heteronymic (cross) Diplopia when the image is projected to the opposite side. At children the Diplopia is noted seldom, apparently, because of active braking of visual impressions of the affected eye.

The research of patients with the Diplopia is conducted in the dark room. Before one eye of the patient put red glass, at distance of 1 — 2 m move a light source (e.g., a lamp with a crack) to the right, to the left, up, from top to bottom and in the intermediate directions. The patient shall watch both eyes, without turning the head, behind movement of a light source and to report about a visible arrangement of double images. Results of a research transfer to the special scheme. In their analysis are guided by the following rules: 1) the muscle of that eye, the image is affected to-rogo departs further from the average horizontal or vertical line; 2) the virtual image is always projected towards action of the paralyzed muscle; therefore D. of the same name arises at damage of lateral direct muscles, heteronymic — at damage of medial direct muscles; 3) the distance between double images increases in process of movement of a look towards action of the affected muscle.

On character of an arrangement of double images it is possible to find out what function of a muscle is broken. It helps the correct diagnosis of a disease of c. N of the page which served as D. Diplopiya's reason — one of symptoms of defeat of a trunk part of a brain at various infectious, toxic and tumoral processes.

Bibliography: The multivolume guide to eye diseases, under the editorship of V. N. Arkhangelsky, t. 3, page 321, M., 1962.

E. S. Avetisov.