PUPILLARY REFLEXES

From Big Medical Encyclopedia

PUPILLARY REFLEXES - the change of diameter of pupils arising in response to photoirritation of a retina at convergence of eyeglobes, accommodations to raznofokusny vision, and also in response to various ekstratseptivny and other irritants.

Frustration 3. the river has special value for diagnosis patol, states.

The size of pupils changes in connection with interaction of two unstriated muscles of an iris: circular, providing narrowing of a pupil (see. Miosis ), and radial, providing its expansion (see. Mydriasis ). The first muscle, sphincter of a pupil (m. sphincter pupillae), is innervated by parasympathetic fibers of a third cranial nerve — preganglionic fibers originate in additional kernels (Yakubovich and Edinger's kernels — Vestfalya), and postganglionic — in a ciliary node.

The second muscle, the dilator of a pupil (m. dilatator pupillae), is innervated by sympathetic fibers — preganglionic fibers originate in the ciliospinal center located in side horns of C8 — Th1 of segments of a spinal cord, postganglionic preferential come out an upper cervical node of a sympathetic boundary trunk and participate in formation of a texture of an internal carotid artery from where they go to an eye.

The irritation of a ciliary node, short ciliary nerves and a third cranial nerve causes the maximum reduction of a pupil.

At defeat of C8 — Th1 of segments of a spinal cord, and also cervical department of a boundary sympathetic trunk is observed narrowing of a pupil and palpebral fissure and an enophthalmos (see. Bernard — Horner a syndrome ). At irritation of these departments the mydriasis is noted. The sympathetic ciliospinal center (centrum ciliospinale) is depending on a subthalamic kernel (Lewis's kernel) since his irritation causes a mydriasis and a palpebral fissure, especially on the opposite side. In addition to the subcrustal pupillary sympathetic center, nek-ry researchers existence of the cortical center admits front departments of a frontal lobe. The conductors which began in the cortical center go to subcrustal where are interrupted, and from there is a new system of conduction fibers going to a spinal cord and undergoing incomplete decussation owing to what the sympathetic pupillary innervation is connected with the centers of both parties. The irritation of some sites an occipital and parietal lobe causes narrowing of a pupil.

Among numerous 3. the river of the most important is a pupillary test on light — direct and consensual. Narrowing of a pupil of the eye which is exposed to lighting carries the name of forward reaction, narrowing of a pupil of an eye at illumination of other eye is called consensual reaction.

Fig. 1. Scheme of reaction of pupils to light. The size of a pupil and its photoharmose is defined by the coordinated functioning of the sympathetic ciliospinal center (11) innervating the dilator of a pupil (2), and parasympathetic dorsal kernels of Yakubovich — Edingera — Vestfalya (9), innervating a sphincter of a pupil (1). Narrowing of a pupil in response to photoirritation is carried out at hit of light on a retina (3), visual signals are transmitted on an optic nerve (4), visual decussation (5) and a path (7) in front dvukholmy (8) where an efferent part of an arch of a pupillary reflex comes to the end. From here through Yakubovich's kernels — Edingera — Vestfalya (9), a ciliate node (6) the impulse reaches a sphincter of a pupil (1). The mydriasis is carried out by the ciliospinal center (11) sending impulses to the dilator of a pupil (2) through an upper cervical sympathetic ganglion (10).

The reflex arc of a pupillary test on light consists of four neurons (tsvetn. fig. 1): 1) photoreceptor cells of a retina which axons as a part of fibers of an optic nerve and a path go to front a dvukholmiya; 2) neurons front a dvukholmiya which axons go to parasympathetic additional kernels (Yakubovich and Edinger's kernels — Vestfalya) third cranial nerves; 3) neurons of parasympathetic kernels which axons go to a ciliary node; 4) the fibers of neurons of a ciliary node going as a part of short ciliary nerves to a sphincter of a pupil.

At a research of pupils first of all pay attention to their size and a form; the size fluctuates depending on age (at advanced age pupils narrower), from extent of illumination of eyes (the lighting is weaker, the diameter of a pupil is wider). Then pass to a research of a pupillary test to light, convergence, accommodation of an eye and reaction of pupils to pain.

The research of forward reaction of pupils on light takes place as follows. In the light room inspected sits down opposite to the doctor so that his face was turned to a light source. Eyes shall be open and evenly lit. The doctor covers both eyes inspected by the hands, then quickly takes away a hand from one eye therefore the pupil is quickly narrowed. After definition of a photoharmose in one eye this reaction is investigated also on other eye.

At a research of consensual reaction of pupils to light close one eye of inspected. When the doctor takes away a hand from an eye, in other eye there is also a narrowing of a pupil. At repeated closing of an eye the pupil of other eye extends.

Reaction of pupils to accommodation consists in narrowing of pupils by consideration of a subject near the person and their expansion at a look afar (see. Accommodation of an eye ). Accommodation at a short distance is followed by convergence of eyeglobes.

Reaction of pupils to convergence — narrowing of pupils at reduction of eyeglobes of a knutra. Usually this reaction is caused approach of the subject fixed by a look. Narrowing is the greatest at approach of a subject to eyes on distance of 10 — 15 cm (see. Convergence of eyes ).

Reaction of pupils to pain consists in their expansion in response to pain stimulation. The reflex center for transfer of these irritations on the muscle expanding a pupil is the subthalamic kernel receiving impulses from a spinotalamichesky path.

The trigeminal pupillary reflex is characterized by small expansion of pupils at irritation of a cornea, conjunctiva a century or the fabrics surrounding an eye, quickly replaced their narrowing. This reflex is carried out thanks to communication of the V pair of cranial nerves with the subcrustal sympathetic pupillary center and a parasympathetic additional kernel of the III pair of nerves.

The Galvanozrachkovy reflex is expressed by narrowing of pupils at action of a galvanic current (the anode is placed over an eye or in a temple, the cathode — in back department of a neck).

Ulitkozrachkovy reflex — bilateral expansion of pupils at unexpected acoustical influences.

Vestibular 3. river, Vodak's reflex — expansion of pupils at irritation of a vestibular mechanism (colorizing, rotation, etc.).

Pharyngeal 3. river — expansion of pupils at irritation of a back wall of a throat. The arch of this reflex passes through glossopalatine and partly wandering (upper guttural) nerves.

Respiratory 3. the river is shown by expansion of pupils at a deep breath and narrowing at an exhalation. The reflex has extreme inconstancy.

A number of the mental moments (a fright, fear, attention etc.) causes a mydriasis; this reaction is considered as a cortical reflex.

Expansion of pupils happens at visualization of night or darkness (Piltts's symptom), and narrowing — at representation of a sunlight or a bright flame (Gaab's symptom).

A number of authors at a research of a condition of pupils used pupillografiya (see). She allows to establish pathology of pupillary tests when at an ordinary research this pathology: it is not found. It is applied: also a pupillografiya with processing: pupillogramm on the COMPUTER.

Various frustration 3. rubles are caused by defeat of peripheral, intermediate and central links of an innervation of muscles of pupils. It meets at many diseases of a brain (infections, first of all syphilis, vascular, tumoral processes, injuries, etc.), upper sites of a spinal cord and a boundary sympathetic trunk, especially its upper cervical node, and also the nervous formations of an eye-socket connected with function of a sphincter and the dilator of a pupil.

At Back tabes and cerebral syphilis Argayll Robertson's syndrome is noted (see. Argayll Robertson syndrome ) and sometimes Govers's symptom — a paradoxical mydriasis during the lighting. At schizophrenia Bumke's symptom — lack of expansion of pupils on pain and mental stimulations can come to light.

At loss of reaction of pupils to light, convergence and accommodation speak about their paralytic immovability; it is connected with disturbance of a parasympathetic innervation of a pupil.


Bibliography: Gordon M. M. Pupillary tests at back to tabes, Works Voyen. - the medical academician of G. M. Kirova, t. 6, page 121, L., 1936; To r about l M. B. and Fedorov E. A. Main neuropathological syndromes, M., 1966; Quietly in V. A. Pupils are normal also of pathology, M., 1953, bibliogr.; Shakhnovich And, R. Mozg and regulation of movements of eyes, M., 1974, bibliogr.; In eh of S. of Die Lehre von den Pupillenbewegungen, V., 1924; Stark L. Neurological control systems, p. 73, N. Y., 1968.

V. A. Smirnov.

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