Syndrome of impaired pupillary reflexes. The study of pupillary reflexes What is the significance of the pupil size reflex

A reflex is a fixed stereotypical response of the body to a certain type of irritation. The implementation of this reaction occurs under the control of the nervous system and does not require the volitional participation of a person. Scheme reflex arc common for all reactions:

perceiving receptors that permeate organs, skin, muscles;
conducting path, which transmits a sensitive impulse to the central nervous system;
command area in the CNS, which may be in the spinal cord or brain;
the central motor part of the arc formed by the executive neuron carrying the command to the executing organs;
the actual organ or tissue that responds to a stimulus.

The absence of the need to think about the action significantly reduces the time from encountering the stimulus to the onset of a response. Many reflexes arose and became fixed in the course of evolution, since they contributed to the survival of our species. One of the most important reactions of the body, which we can also observe, is the pupillary reflex.

The pupil is the "window" into the inner space of the eye. This hole in the iris is designed to regulate the amount of light that will eventually reach the retina. In the most reduced state, its size is 2 mm, and when expanded, it is 7.3 mm. Due to the ability of the pupil to filter out the rays incident on the periphery of the lens, compensation is achieved spherical aberration(elimination of concentric glow around objects), as well as protection of the retina from light burn.

The reaction of the pupils to light is expressed in their constriction (miosis) in bright light and expansion (mydriasis) at dusk. A significant increase in the diameter of the hole worsens color perception and quality of vision, but increases the susceptibility of the eyes to light. Therefore, at dusk, in the presence of a weak source of illumination, we are able to distinguish silhouettes and navigate in space. Dilation (expansion) also partially occurs when there are no factors that cause its narrowing.

A sudden or gradual increase in the level of illumination leads to a reflex constriction of the pupils. Thus, the protection of the retina and other structures of the eye is realized.

The reflex mechanism can be direct and friendly. The hole narrows when it is directly illuminated, and also equally decreases in size in collaboration with the pupil of the other eye, which is affected by light.

As you can see great importance has the ability of the pupil to change its diameter. A decrease in its size occurs with a contraction of the annular, and an increase in the radial muscle fibers that surround the opening of the sphincter. The pupillary reflex is possible because these muscle fibers are controlled by the nerve fibers of the oculomotor nerve. The contraction occurs under the influence of the parasympathetic (mediator acetylcholine), and the expansion - sympathetic (mediator adrenaline) nervous system.

The pupillary reflex arc is a sequence of the following components:

receptors - cells central region the retina, whose axons give rise to the optic nerve;
the path leading to the centers in the CNS, formed by the axons of the neurons of the optic tract;
intercalary neurons are represented by axons of the Yakubovich-Westphal-Edinger nuclei. The primary visual center is located in the cells of the lateral geniculate body. The center of the pupillary reflex is located in the occipital lobe of the brain;
the executive part of the arc is represented by axons of the oculomotor nerve;
target organ - radial and concentric muscle fibers.

A. motor way; B. sensitive path of the reflex arc

The existence of the pupillary reflex arc allows it to narrow already after 0.4 s after exposure to the light flux.

It should also be noted that the diameter of the pupils decreases with eye strain, when it is necessary to focus on very close objects, and expands when looking at the distant plan. The maximum concentration of the light flux on the central fovea of the retina allows you to achieve the best vision. This phenomenon is called the pupillary reflex to accommodation and convergence.

reflex response

Other stimuli are also capable of causing a change in the diameter of the pupils, which become the beginning of the path of the pupillary reflex.

For example, pain, causing the release of adrenaline, causes the physiological expansion of the pupils. The transmission of irritation from nociceptors (pain receptors) to the muscles that control the pupil occurs in the subthalamic nucleus of the brain.

A decrease in the level of oxygen in the blood (asphyxia) leads to reflex pupillary dilation.

Signals from irritation of the cornea, conjunctiva, eyelid tissue also trigger this reflex, which is expressed in a slight expansion of the pupil. Then there is a rapid decrease in its diameter.

Expand the pupil signals from the ear (an unexpected auditory effect), the vestibular apparatus. Pupillary reaction observed when stimulated rear surface throats. AT this case t receptors and the sensitive part of the reflex arc are represented by the glossopharyngeal and laryngeal nerves.

Some drugs (atropine sulfate) are able to block the transmission of nerve impulses along the parasympathetic nerves, as a result of which the pupils also dilate.

The value of the pupillary reflex is very important in the diagnosis of lesions of the peripheral, intermediate and central links of innervation. The timing of the onset, the degree of contraction and dilation, the symmetry of the pupils, or the lack of reaction to light may indicate diseases that have damaged the brain or spinal cord. Most often this infectious diseases, vascular pathologies, tumor process, injuries of the occipital part of the brain, top spinal cord, sympathetic trunk, nerve plexuses of the orbit.

Possible violations

Many of us know from films that even without consciousness, a person retains a pupillary reaction to light, but with brain death it disappears. In addition, there are other reasons for the violation of the reflex.

Anisocoria - pupils of different sizes, since one of the oculomotor nerves is affected. For example, Argyll-Robertson syndrome describes a severe and uneven constriction of pupils that do not respond to light when the nerves are affected by tertiary syphilis, diabetes, chronic alcoholism, encephalitis.
Amaurotic immobility- complete absence of pupillary reflex to direct illumination. It develops against the background of a disease of the retina (amaurosis), which is characterized by blindness without visible ophthalmic pathologies. He is more on the side of the blind eye, retains a friendly reaction. A healthy organ has a direct reaction, but no friendly one. The convergence reflex was preserved in both eyes.
Hemianopic immobility of the pupil- occurs when the optic tract is damaged in the area of the intersection of the nerves. Pupillary reactions are preserved only in response to light entering the temporal areas of the retina. When illuminating the nasal areas, there is no direct and indirect reflex. The convergence reflex is preserved.
Reflex immobility- the absence of a direct and friendly reaction of the pupils in case of damage to the parasympathetic innervating nerves, but with the preservation of the reflex during convergence and accommodation.
Absolute immobility of the pupil- complete absence of physiological reactions of mydriasis and miosis. Occurs against the background of inflammation in the nucleus, root or trunk of the oculomotor and ciliary nerves.
Sympathetic disorders. The pathology of the dark pupillary reflex (miosis due to paralysis of the radial muscles, impaired pupillary dilation at dusk) arises from damage to the preganglionic and postganglionic fibers during birth trauma(especially the brachial plexus), trunk aneurysm carotid artery, inflammatory diseases in the eye area.

Other reactions

Asthenic - the onset of "fatigue" of the pupils until the constriction completely refuses to repetitive exposure to light. It develops from infectious, somatic, neurological diseases and poisonings.
Paradoxical - very rare pathology. In this state, the pupils constrict in the dark, and dilate in the light. May occur after a stroke, against the background of hysteria.
Tonic - slow pupil dilation against the background of high excitability of parasympathetic nerves. Usually found in alcoholics.
Increased - more active constriction of the pupil in the light. It is a consequence of concussion, psychosis, Quincke's edema, bronchial asthma.
Premortal - special kind pupillary reflex. At the approach of death, the pupils become very narrow, and then mydriasis (dilation) begins to progress without the presence of a reflex contraction to light.

The study of the pupillary reflex provides a broad basis for diagnosing the state of the nervous system and the whole organism as a whole.

The eyes are enough important body for the normal functioning of the body and a full life. The main function is the perception of light stimuli, due to which the picture appears.

Structural features

This peripheral organ of vision is located in a special cavity of the skull, which is called the orbit. From the sides of the eye is surrounded by muscles, with the help of which it is held and moved. The eye consists of several parts:

Directly the eyeball, which has the shape of a ball about 24 mm in size. It consists of the vitreous body, the lens and aqueous humor. All this is surrounded by three shells: protein, vascular and mesh, arranged in reverse order. The elements that make up the picture are located on the retina. These elements are receptors that are sensitive to light;
The protective apparatus, which consists of the upper and lower eyelids, the orbit;
adnexal apparatus. The main components are the lacrimal gland and its ducts;
The oculomotor apparatus, which is responsible for the movements of the eyeball and consists of muscles;

Main functions

The main function that vision performs is to distinguish between various physical characteristics of objects, such as brightness, color, shape, size. In combination with the action of other analyzers (hearing, smell, and others), it allows you to adjust the position of the body in space, as well as determine the distance to the object. That's why prevention eye diseases should be carried out with enviable regularity.

Presence of a pupillary reflex

With the normal functioning of the organs of vision, with certain external reactions, the so-called pupillary reflexes occur, in which the pupil narrows or expands. The pupillary reflex, the reflex arc of which is the anatomical substrate of the pupil's reaction to light, indicates the health of the eyes and the whole organism as a whole. That is why, in some diseases, the doctor first checks for the presence of this reflex.

What is a reaction?

The pupil reaction or the so-called pupillary reflex (other names are the iris reflex, irritant reflex) is some change in the linear dimensions of the pupil of the eye. Constriction is usually caused by contraction of the muscles of the iris, and the reverse process - relaxation - leads to the expansion of the pupil.

Possible reasons

This reflex is caused by a combination of certain stimuli, the main of which is a change in the level of illumination of the surrounding space. In addition, a change in the size of the pupil can occur for the following reasons:

action of a number of drugs. That is why they are used as a way to diagnose the state of drug overdose or excessive depth of anesthesia;
changing the point of focus of a person's view;
emotional outbursts, both negative and positive equally.

If there is no reaction

Lack of pupil reaction to light may indicate various human conditions that pose a threat to life and require immediate intervention by specialists.

Diagram of the pupillary reflex

The muscles that control the work of the pupil can easily influence its size if they receive a certain stimulus from the outside. This allows you to control the amount of light that enters the eye directly. If you close your eyes from those who come sun rays, and then open it, the pupil, which previously expanded in the dark, immediately decreases in size when the light appears. The pupillary reflex, the reflex arc of which begins on the retina, indicates the normal functioning of the organ.

The iris has two types of muscles. One group is circular muscle fibers. They are innervated by parasympathetic fibers ophthalmic nerve. If these muscles contract, this process causes pupil constriction. The other group is responsible for pupil dilation. It includes radial muscle fibers that are innervated by sympathetic nerves.

The pupillary reflex, the scheme of which is quite typical, occurs in the following order. Light that passes through the layers of the eye and is refracted in them hits the retina directly. The photoreceptors that are located here, in this case, are the beginning of the reflex. In other words, this is where the path of the pupillary reflex begins. The innervation of the parasympathetic nerves affects the work of the sphincter of the eye, and the arc of the pupillary reflex contains it in its composition. The process itself is called the efferent shoulder. The so-called center of the pupillary reflex is also located here, after which various nerves change their direction: some of them go through the legs of the brain and enter the orbit through the upper fissure, others - to the sphincter of the pupil. This is where the path ends. That is, the pupillary reflex closes. The absence of such a reaction may indicate any disturbances in the human body, which is why it is given such great importance.

Pupillary reflex and signs of its defeat

When examining this reflex, several characteristics of the reaction itself are taken into account:

pupil constriction;
the form;
the uniformity of the reaction;
pupillary mobility.

There are several of the most popular pathologies, indicating that the pupillary and accommodative reflexes are impaired, which indicates malfunctions in the body:

Amaurotic immobility of the pupils. This phenomenon represents a loss of a direct reaction when illuminating a blind eye and a friendly reaction if vision problems are not observed. The most common causes are various diseases of the retina itself and the visual pathway. If the immobility is unilateral, is a consequence of amaurosis (retinal damage) and is combined with pupil dilation, albeit insignificant, then there is a possibility of developing anisocoria (pupils become different sizes). With such a violation, other pupillary reactions are not affected in any way. If amaurosis develops on both sides (that is, both eyes are affected at the same time), then the pupils do not react in any way and even when exposed to sunlight remain dilated, that is, the pupillary reflex is completely absent.
Another type of amaurotic immobility of the pupils is hemianopic immobility of the pupil. Perhaps there is a lesion of the visual tract itself, which is accompanied by hemianopia, that is, blindness of half of the visual field, which is expressed by the absence of a pupillary reflex in both eyes.

Reflex immobility or Robertson's syndrome. It consists in the complete absence of both direct and friendly reaction of the pupils. However, unlike the previous type of lesion, the reaction to convergence (narrowing of the pupils if the gaze is focused on a certain point) and accommodation (changes in the external conditions in which the person is located) is not impaired. This symptom due to the fact that changes occur in the parasympathetic innervation of the eye in the case when there is damage to the parasympathetic nucleus, its fibers. This syndrome may indicate the presence of a severe stage of syphilis of the nervous system, less often the syndrome reports encephalitis, a brain tumor (namely, in the area of \u200b\u200bthe legs), and also a traumatic brain injury.

The reasons may be inflammatory processes in the nucleus, root or trunk of the nerve responsible for eye movements, a focus in the ciliary body, tumors, abscesses of the posterior ciliary nerves.

The anatomical structure of the visual pathway is quite complex and includes a number of neural links. Within the retina of each eye, this is a layer of rods and cones (I neuron), then bipolar (II neuron) and ganglion cells with their long axons (III neuron). Together they form the peripheral part of the optic pathway, represented by the optic nerves, chiasm, and optic tracts. The latter terminate in the cells of the lateral geniculate body, which plays the role of the primary visual center. The fibers of the central neuron of the visual pathway (radiatio optica) already originate from them, which reach the area striata of the occipital lobe of the brain. The primary cortical center of the visual analyzer is localized here.

Optic nerve (n.opticus) begins with a disk formed by the axons of the retinal ganglion cells and ends in the chiasm. Its total length varies in adults from 35 to 55 mm. A significant part of the nerve is the orbital segment (25-30 mm), which in the horizontal plane has an S-shaped bend, due to which it does not experience tension during movements of the eyeball.

For a considerable length (from the exit from the eyeball to the entrance to the canalis opticus), the nerve, like the brain, has three shells: hard, arachnoid and soft. Together with them, its thickness is 4-4.5 mm, without them - 3-3.5 mm. In the eyeball, the dura mater fuses with the sclera and Tenon's capsule, and in the optic canal, with the periosteum. The intracranial segment of the nerve and chiasm, located in the subarachnoid chiasmatic cistern, are dressed only in a soft shell.

The intrathecal spaces of the ophthalmic part of the nerve (subdural and subarachnoid) connect with similar spaces in the brain, but are isolated from each other. They are filled with a liquid of complex composition (intraocular, tissue, cerebrospinal fluid). Since the intraocular pressure is normally twice the intracranial pressure (10-12 mm Hg), the direction of its current coincides with the pressure gradient. The exception is when there is a significant increase in intracranial pressure(for example, with the development of a brain tumor, hemorrhages in the cranial cavity) or, conversely, the tone of the eye decreases sharply.

All nerve fibers that make up the optic nerve are grouped into three main bundles. Axons of ganglion cells extending from the central (macular) region of the retina constitute the papillomacular bundle, which enters the temporal half of the optic nerve head. Fibers from the ganglion cells of the nasal half of the retina go along radial lines to the same half of it. Similar fibers, but from the temporal half of the retina, on the way to the optic nerve head “flow around” the papillomacular bundle from above and below.

In the orbital segment of the optic nerve near the eye, the ratios between the nerve fibers remain the same as in its disk. Next, the papillomacular bundle moves to the axial position, and the fibers from the temporal and nasal halves of the retina move to the corresponding parts of the optic nerve.

Thus, the optic nerve is clearly divided into right and left halves. Its division into upper and lower halves is less pronounced. An important clinical feature is that the nerve is devoid of sensitive nerve endings.

In the cranial cavity, the optic nerves connect above the sella turcica, forming chiasma (chiasma opticum), which is covered with a pia mater and has the following dimensions: length - from 4 to 10 mm, width - 9-11 mm and thickness 5 mm. It borders below on the diaphragm of the sella turcica (a preserved section of the dura mater), above (in the posterior section) - on the bottom of the third ventricle, on the sides - on the internal carotid arteries, and on the back - on the funnel of the pituitary gland.

In the region of the chiasm, the fibers of the optic nerves partially cross due to portions associated with the nasal halves of the retinas. Moving to the opposite side, they connect with fibers from the temporal halves of the retinas of the other eye and form the visual tracts. Here, the papillo-macular bundles also partially intersect.

The optic tracts begin at the posterior surface of the chiasma and, rounding the brain stem from the outside, end in the lateral geniculate body (corpus geniculatum laterale), the posterior part of the optic tubercle (thalamus opticus) and the anterior quadrigemina (corpus quadrigeminum anterius) of the corresponding side. However, only the external geniculate bodies are the unconditional subcortical visual center. The remaining two formations perform other functions.

In the visual tracts, whose length in an adult reaches 30-40 mm, the papillomacular bundle also occupies a central position, and the crossed and non-crossed fibers still go in separate bundles. At the same time, the first of them are located ventro-medially, and the second - dorso-laterally.

Visual radiation (fibers of the central neuron) starts from the ganglion cells of the fifth and sixth layers of the lateral geniculate body. First, the axons of these cells form the so-called field of Wernicke (Wernicke), and then, passing through the posterior thigh of the internal capsule, fan-shaped diverge in the white matter of the occipital lobe of the brain. The central neuron ends in the furrow of the bird's spur (sulcus calcarinus). This area personifies the sensory visual center - the 17th cortical field according to Brodmann.

pupillary reflex path- light and the installation of eyes at a close distance is quite difficult. The afferent part of the reflex arc of the first of them starts from cones and rods of the retina (according to some sources, only from cones) in the form of autonomous fibers that go as part of the optic nerve. In the chiasm, they cross in exactly the same way as the optic fibers and pass into the optic tracts. In front of the external geniculate bodies, the pupillomotor fibers leave them and, after a partial decussation, continue into the brachium quadrigeminum, where they end at the cells of the so-called pretectal region (area pretectalis). Further, new, interstitial neurons, after partial decussation, are sent to the corresponding nuclei (Jakubovich-Edinger-Westphal) of the oculomotor nerve. afferent fibers from yellow spot the retinas of each eye are represented in both oculomotor nuclei.

The efferent path of innervation of the sphincter of the iris starts from the already mentioned nuclei and goes in a separate bundle as part of n.oculomotorius. In the orbit, the sphincter fibers enter its lower branch, and then through the radix oculomotoria into the ciliary node. Here the first neuron of the considered path ends and the second one begins. Upon exiting the ciliary node, the sphincter fibers in the nn. ciliares breves, having pierced the sclera, enter the perichoroidal space, where they form the nerve plexus. Its terminal branches penetrate the iris and enter the muscle in separate radial bundles, i.e. innervate it sectorally. In total, there are 70-80 such segments in the sphincter of the pupil.

The efferent pathway for the m.dilatator pupillae, which receives sympathetic innervation, starts from the ciliospinal center Budge. The latter is located in the anterior horns of the spinal cord between the VII cervical and II thoracic vertebrae. Connecting branches depart from here, which through the border trunk of the sympathetic nerve (l), and then the lower and middle sympathetic cervical ganglia (ti and t2) reach the upper ganglion (level II-IV of the cervical vertebrae). Here the first neuron of the path ends and the second begins, which is part of the plexus of the internal carotid artery. In the cranial cavity, the fibers innervating the pupillary dilator exit from the mentioned plexus, enter the gangl.trigeminale, and then leave it as part of the n.ophthalmicus. Already at the top of the orbit, they pass into n.nasociliaris and then, together with nn.ciliares longi, penetrate into the eyeball. In addition, the central sympathetic path (s) also departs from the Budge center, ending in the cortex of the occipital lobe of the brain. From here begins the cortico-nuclear path of inhibition of the sphincter of the pupil.

In bright light, the pupil constricts; in weak light, the pupil dilates.

A change in the size of the pupil occurs due to the work of the muscles of the iris: the sphincter and dilator. The iris sphincter (narrows the pupil) is represented by smooth muscle fibers located circularly in the pupillary part of the iris, innervated by the parasympathetic nervous system, and the dilator (expands the pupil) is represented by smooth muscle fibers located radially in the ciliary zone of the iris, innervated by the sympathetic nervous system (Figure 1).

The mechanism of the pupillary reflex

The first link of the pupillary reflex is photoreceptors: rods and cones. They contain pigments, after the activation of the pigment by light, a chain chemical reaction, leading to the formation of a nerve impulse transmitted from photoreceptor cells to other retinal cells: bipolar, amacrine, ganglionic, then along the axons of ganglion cells that form the optic nerve, the impulse reaches the chiasm.

Chiasma - optic chiasm, where part of the fibers of the right optic nerve pass to left side, and part of the fibers of the left optic nerve - to the right. In dogs, the amount of "transferring" fibers is 75%, in cats 63%. After the chiasm, the impulse continues to be transmitted along the optic tract, most of fibers (80%) goes to the lateral geniculate nucleus and then transmits a signal for the formation of a visual image.

However, 20% of the fibers of the optic tract separate before reaching the lateral geniculate nucleus and go to the pretectal nucleus of the midbrain, where synapse occurs. The axons of the pretectal cells go to the parasympathetic nucleus of the oculomotor nerve (Edinger-Westphal nucleus), some of the fibers cross and go to the opposite Edinger-Westphal nucleus.

Parasympathetic axons emerge from the Edinger-Westphal nucleus and, as part of the oculomotor / oculomotor nerve (CN III), go to the orbit. There is a ciliary ganglion in the orbit, where the synapse occurs, postganglionic fibers as part of short ciliary nerves enter the eyeball and innervate the iris sphincter (Figure 2).

In dogs short ciliary nerves are distributed evenly over the iris, and in cats- first they are divided into 2 branches: temporal and nasal, with an isolated lesion of one of the branches, a D-shaped or back-D-shaped pupil appears in cats.

A normal pupillary reflex indicates the possibility of transmitting an impulse from the retina along the optic nerve through the chiasm along only 20% of the fibers of the optic tract, in some areas of the midbrain and on the function of the parasympathetic fibers of the oculomotor nerve.

Important to remember, that for vision it is necessary not only for an impulse to go from the retina along the nerve to the chiasm, but also for it to arrive 80% of the fibers of the optic tract in the visual cortex. Therefore, if parts of the visual tracts and visual cortex are damaged, there will be no vision, and the pupillary reflex will be normal.

Pupillary reflex evaluation is usually done using white light from a flashlight pen or transilluminator or slit lamp. Normally, the pupil quickly constricts in response to a light stimulus (direct reflex), while the pupil of the other eye constricts at the same time (friendly reflex). Slow, incomplete, absent direct or friendly pupillary reflex is a consequence of a violation in the transmission of an impulse from the retina to the brain or from the brain along the oculomotor nerve.

midriaz- dilation of the pupil and the absence of a pupillary reflex, may be under the following conditions:

Damage to the oculomotor nerve, while the eye is sighted
Atrophy of the iris, while the eye is sighted
The use of mydriatics, while the eye is sighted
Damage to the retina (detachment), while the eye is blind
Damage to the optic nerve (neuritis, rupture, damage in glaucoma), while the eye is blind
The defeat of the chiasm (neoplasm, inflammation, trauma), bilateral blindness and bilateral mydriasis are characteristic.

Pupillary reflexes- a change in the diameter of the pupils that occurs in response to light stimulation of the retina, with convergence eyeballs, accommodation to multifocal vision, as well as in response to various extraceptive and other stimuli.

Disorder 3. r. is of particular importance for the diagnosis of patol, conditions.

The size of the pupils changes due to the interaction of two smooth muscles of the iris: the circular one, which provides constriction of the pupil (see Miosis), and the radial one, which provides its expansion (see Mydriasis). The first muscle, the pupil sphincter (m. sphincter pupillae), is innervated by parasympathetic fibers of the oculomotor nerve - preganglionic fibers originate in accessory nuclei (Yakubovich and Edinger-Westphal nuclei), and postganglionic fibers in the ciliary node.

The second muscle, the pupil dilator (m. dilatator pupillae), is innervated by sympathetic fibers - the preganglionic fibers originate in the ciliospinal center located in the lateral horns of the C8 - Th1 segments of the spinal cord, the postganglionic fibers predominantly come out of the upper cervical node sympathetic border trunk and participate in the formation of the plexus of the internal carotid artery, from where they are sent to the eye.

Irritation of the ciliary node, short ciliary nerves and the oculomotor nerve causes maximum pupil contraction.

With damage to the C8-Th1 segments of the spinal cord, as well as cervical border sympathetic trunk there is a narrowing of the pupil and palpebral fissure and enophthalmos (see Bernard-Horner syndrome). With irritation of these departments, pupil dilation is noted. The sympathetic ciliospinal center (centrum ciliospinale) is dependent on the subthalamic nucleus (Lewis nucleus), since its irritation causes dilation of the pupil and palpebral fissure, especially on the opposite side. In addition to the subcortical pupillary sympathetic center, some researchers recognize the existence of a cortical center in the anterior sections of the frontal lobe. The conductors that began in the cortical center go to the subcortical center, where they are interrupted, and from there arises new system conductor fibers, going to the spinal cord and undergoing incomplete decussation, as a result of which the sympathetic pupillary innervation is associated with the centers of both sides. Irritation of some areas of the occipital and parietal lobes causes pupil constriction.

Among the numerous 3. p. the most important is the pupillary reaction to light - direct and friendly. The constriction of the pupil of the eye exposed to illumination is called the direct reaction, the constriction of the pupil of the eye when the other eye is illuminated is called the consensual reaction.

The reflex arc of the pupillary reaction to light consists of four neurons (printing. Fig. 1): 1) photoreceptor cells of the retina, the axons of which are part of the fibers optic nerve and the tract go to the anterior colliculus; 2) neurons of the anterior colliculus, the axons of which are directed to the parasympathetic accessory nuclei (nuclei of Yakubovich and Edinger-Westphal) of the oculomotor nerves; 3) neurons of the parasympathetic nuclei, the axons of which go to the ciliary ganglion; 4) fibers of neurons of the ciliary ganglion, which go as part of short ciliary nerves to the sphincter of the pupil.

In the study of pupils, first of all, pay attention to their size and shape; the size varies depending on age (in older age, the pupils are narrower), on the degree of illumination of the eyes (the weaker the illumination, the wider the pupil diameter). Then they proceed to the study of the pupillary reaction to light, convergence, accommodation of the eye and the reaction of the pupils to pain.

The study of the direct reaction of pupils to light is as follows. In a bright room, the subject sits opposite the doctor so that his face is turned to the light source. Eyes should be open and evenly lit. The doctor covers both eyes of the subject with his hands, then quickly removes his hand from one eye, as a result of which the pupil quickly narrows. After determining the reaction to light in one eye, this reaction is examined in the other eye.

When examining the friendly reaction of pupils to light, one eye of the subject is closed. When the doctor removes the hand from the eye, pupil constriction also occurs in the other eye. When the eye is closed again, the pupil of the other eye dilates.

The reaction of the pupils to accommodation consists in the constriction of the pupils when considering an object near the face and their expansion when looking into the distance (see Accommodation of the eye). Accommodation at close range is accompanied by convergence of the eyeballs.

The pupillary reaction to convergence is the constriction of the pupils when the eyeballs are brought inwards. Usually this reaction is caused by the approach of an object fixed by the eye. The narrowing is greatest when the object approaches the eyes at a distance of 10-15 cm (see Convergence of the eyes).

The reaction of the pupils to pain is their expansion in response to pain stimulation. The reflex center for transmitting these stimuli to the muscle that dilates the pupil is the subthalamic nucleus, which receives impulses from the spinothalamic tract.

The trigeminal pupillary reflex is characterized by little extension pupils with irritation of the cornea, conjunctiva of the eyelids or tissues surrounding the eye, quickly followed by their narrowing. This reflex is carried out due to the connection of the V pair cranial nerves with a subcortical sympathetic pupillary center and a parasympathetic accessory nucleus of the third pair of nerves.

The galvano-pupillary reflex is expressed by the constriction of the pupils under the action of a galvanic current (the anode is placed above the eye or in the temple area, the cathode is placed in the back of the neck).

The snail pupil reflex is a bilateral expansion of the pupils during unexpected auditory influences.

Vestibular 3. p., Vodak's reflex, - dilation of the pupils with irritation of the vestibular apparatus (calorization, rotation, etc.).

Pharyngeal 3. r. - dilated pupils when irritated rear wall throats. The arc of this reflex passes through the glossopharyngeal and partly vagus (upper laryngeal) nerves.

Respiratory 3. p. It is manifested by the expansion of the pupils with a deep breath and narrowing with exhalation. The reflex is extremely inconsistent.

A number of mental moments (fright, fear, attention, etc.) cause pupil dilation; this reaction is considered as a cortical reflex.

The dilation of the pupils occurs with the mental representation of night or darkness (Piltz symptom), and the constriction occurs with the representation sunlight or a bright flame (Gaab's symptom).

A number of authors in the study of the state of the pupils used pupillography (see). It allows you to establish the pathology of pupillary reactions in those cases when this pathology is not detected during a conventional study: It is used: also pupillography with processing: pupillogram on a computer.

Various frustration 3. river. are caused by damage to the peripheral, intermediate and central links of the innervation of the muscles of the pupils. This occurs in many diseases of the brain (infections, primarily syphilis, vascular, tumor processes, injuries, etc.), the upper sections of the spinal cord and the borderline sympathetic trunk, especially its upper cervical node, as well as nerve formations eye sockets associated with the function of the sphincter and dilator of the pupil.

With dorsal tabes and cerebral syphilis, Argyll Robertson's syndrome is noted (see Argyll Robertson's syndrome) and sometimes Govers's symptom is a paradoxical dilation of the pupil when illuminated. With schizophrenia, Bumke's symptom can be detected - the absence of dilation of the pupils for painful and mental irritations.

With the loss of the reaction of the pupils to light, convergence and accommodation, they speak of their paralytic immobility; it is associated with a violation of the parasympathetic innervation of the pupil.

Bibliography: Gordon M. M. Pupillary reactions in spinal dryness, Proceedings of the Military. acad. them. G. M. Kirov, vol. 6, p. 121, L., 1936; To r about l M. B. and Fedorova E. A. Basic neuropathological syndromes, M., 1966; Smirno in V. A. Pupils are normal and pathological, M., 1953, bibliogr.; Shakhnovich A, R. Brain and regulation of eye movements, M., 1974, bibliogr.; In eh Mr. C. Die Lehre von den Pupillenbewegungen, B., 1924; Stark L. Neurological control systems, p. 73, N.Y., 1968.

V. A. SMIRNOV