Pupillary reflex and signs of its defeat

Eyes are quite an important organ for the normal functioning of the body and a full life. The main function is the perception of light stimuli, thanks to which the picture appears.

Features of the structure

This peripheral organ of vision is located in a special cranium cavity, which is called the eye socket. The sides of the eyes are surrounded by muscles, through which he holds and moves. It consists of several parts:

1. The eyeball itself, which has the shape of a ball about 24 mm in size. It consists of a vitreous, crystalline and watery moisture. All this is surrounded by three shells: protein, vascular and reticulate, arranged in the reverse order. Elements, through which the picture is obtained, are located on the mesh shell. These elements are receptors that are sensitive to light;
2. The protective apparatus, which consists of the upper and lower eyelids, the orbit;
3. Attachment device. The main components are the lacrimal gland and its ducts;
4. The oculomotor apparatus, which is responsible for the movement of the eyeball and consists of muscles;
5. The optic nerve.

Main functions

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

Presence of pupillary reflex

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

What is a reaction?

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

Possible reasons

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

• Action of a number of medicines. That is why they are used as a way of diagnosing the state of drug overdose or excessive depth of anesthesia;
• Change the focus point of view of a person;
• Emotional outbursts, both negative and positive in equal measure.

If there is no reaction

The absence of a pupil's reaction to light can indicate different states of a person that pose a danger to life and require immediate intervention by specialists.

Pupillary reflex

Muscles that control the pupil's work can easily influence its magnitude if a certain stimulus from outside has acted on them. This allows you to regulate the flow of light that enters directly into the eye. If the eye is covered from incoming sunlight and then opened, the pupil, which previously expanded in the dark, immediately diminishes in size when light appears. The pupillary reflex, the reflex arc of which begins on the retina, indicates the normal functioning of the organ.

Iris has two types of muscles. One group is represented by circular muscle fibers. Innerviruyut their parasympathetic fibers of the optic nerve. If these muscles contract, then this process causes a narrowing of the pupil. Another group is responsible for the dilatation of the pupil. It includes radial muscle fibers that are innervated by sympathetic nerves.

The pupillary reflex, whose pattern is quite typical, occurs in the following order. The light that passes through the layers of the eye and is refracted in them, falls directly on the retina. Photoreceptors, which are located here, in this case are the beginning of the reflex. In other words, it is here that the path of the pupillary reflex begins. The innervation of the parasympathetic nerves affects the operation of the sphincter of the eye, and the arch of the pupillary reflex contains it in its composition. The process itself is called the efferent shoulder. There is also the so-called center of pupillary reflex, after which various nerves change their direction: some of them go through the legs of the brain and enter the orbit through the upper slit, others - to the sphincter of the pupil. This ends the way. That is, the pupillary reflex is closed. The absence of such a reaction may indicate any violations in the human body, which is why this is given so much importance.

Pupillary reflex and signs of its defeat

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

• The size of the narrowing of the pupil;
• the form;
• The uniformity of the reaction;
• Pupillary mobility.

There are several most common pathologies that indicate that pupillary and accommodative reflexes are impaired, which indicates a malfunction in the body:

• Amavrotic motionless pupils. This phenomenon is a direct reaction when the blind eye is illuminated and the reaction is friendly, if the vision of problems is not observed. The most common causes are various diseases of the retina itself and the visual pathway. If the immobility is one-sided, is a consequence of amaurosis (lesion of the retina) and is combined with the dilatation of the pupil, although insignificant, then there is a possibility of anisocoria (the pupils become of different sizes). With such a violation, other pupillary reactions are not affected in any way. If the amaurosis develops on both sides (that is, both eyes are simultaneously affected), the pupils do not react at all and even when exposed to the sunlight they remain enlarged, that is, the pupillary reflex is completely absent.
• Another type of amaurotic immobility of the pupils is the hemianopic immobility of the pupil. Perhaps the defeat of the visual tract itself is observed, which is accompanied by hemianopsia, that is, blindness of the half of the visual field, which is expressed by the absence of a pupillary reflex in both eyes.

• Reflexive 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 (the narrowing of the pupils in the event that the view is focused on a certain point) and the accommodation (the change in the external conditions in which the person is located) is not violated. This symptom is due to the fact that there are changes in the parasympathetic innervation of the eye in the event that there is a lesion of the parasympathetic nucleus, its fibers. This syndrome can indicate the presence of a severe stage of syphilis of the nervous system, less often the syndrome reports on encephalitis, brain tumors (namely, in the legs), and also about craniocerebral trauma.

• Absolute, or complete immobility of the pupil (that is, it does not narrow, and does not expand at all). When a beam of light beams is applied to the pupil, the absence of both direct and friendly reaction to the stimulus is diagnosed. This reaction develops not instantaneously, but gradually. As a rule, it starts with a violation of physiological pupillary reactions - mydriasis (dilated pupil), lack of pupillary mobility.

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