eyes are rather important body for the normal functioning of the body and fulfilling life.The main function - the perception of light stimuli, and so the picture appears.
located the peripheral eyesight in a special cavity of the skull, which is called the orbit.On both sides surrounded by the eye muscles, by which it is held and moved.It consists of several parts of the eye:
- Just eyeball, which is a sphere of about 24 mm.It consists of vitreous, lens and aqueous humor.All of this is surrounded by three membranes: the protein, vascular and netted, placed in reverse order.The elements that make the picture turns out, are located on the retina.These elements are the receptors that are sensitive to light;
- protective device, which consists of the upper and lower eyelids, orbit;
- adnexa.The main components are the lacrimal gland and its ducts;
- oculomotor system, which is responsible for the movement of the eyeball composed of muscles;
- optic nerve.
main function, which performs vision - distinguishing the different physical characteristics of objects, such as brightness, color, shape, size.In conjunction with the action of other analyzers (hearing, smell, etc.) allows you to adjust the position of the body in space, as well as to determine the distance to the subject.That is why the prevention of eye diseases should be carried out with enviable regularity.
Availability pupillary reflex
In normal operation of the organs of vision, under certain external reactions occur so-called pupillary reflexes in which the pupil narrows or expands.Pupillary reflex, reflex arc which is the anatomical substrate of the reaction of the pupil to light, indicates the health of the eyes and the whole body.That's why in some diseases the doctor first of all checks this reflex.
What is the reaction?
reaction of the pupil or the so-called pupillary reflex (other names - raduzhkovy reflex iritichesky reflex) is some change in the linear dimensions of the pupil of the eye.The restriction is usually caused by contraction of the muscles of the iris, and the reverse process - relaxation - leads to dilation of the pupils.
Called the jerk combination of specific stimuli, most of which is considered to change the level of illumination of the surrounding space.In addition, dimensional change of the pupil may occur for the following reasons:
- effect of several drugs.That is why they are used as a way to diagnose the state of an overdose of drugs or excessive depth of anesthesia;
- change the focus point of view of human rights;
- emotional outbursts, with both negative and positive alike.
If no response
lack of reaction of the pupil to light may indicate different states of people who are a danger to life and requires immediate intervention specialists.
scheme pupillary reflex
muscles, which control the pupil can easily affect its value, if they did certain stimulus from the outside.This allows you to regulate the influx of light that comes directly into the eye.If the eye shield from incoming sunlight, and then open it, the pupil, which is pre-grown in the dark, just shrinks the appearance of light.Pupillary reflex, reflex arc that begins in the retina, indicates normal functioning of the body.
Iris has two types of muscles.One group is a circular muscle fibers.Innervated by parasympathetic fibers of the optic nerve.When these muscles contract, this process causes constriction of the pupil.Another group is responsible for the expansion of the pupil.It consists of radial muscle fibers that are innervated by sympathetic nerves.
Pupillary reflex circuit is quite typical, in the following order.The light that passes through the layers of the eye and refracted therein falls directly on the retina.Photoreceptors which there are arranged, in this case are the beginning reflex.In other words, this is where the path begins, and pupillary reflex.The innervation of the parasympathetic nerves affects the eye sphincter and pupillary reflex arc includes it in its composition.The process itself is called the efferent arm.There is also the so-called center of the pupillary reflex, after which various nerves change their direction: some of them go through the brain stem and enter the orbit through the upper slot, the other - to the sphincter of the pupil.On this path ends.That is, the pupillary reflex closes.The absence of such a reaction may indicate any violations of the human body, which is why it attaches so much importance.
Pupillary reflex and signs of defeat
The examination of this reflex is taken into account several characteristics of the reaction:
- value of pupil constriction;
- uniformity of the reaction;
- mobility of pupils.
There are a few of the most popular pathologies, indicating that the accommodation and the pupillary reflexes are violated, indicating that the fault in the body:
- Amavroticheskaya immobility of the pupils.This phenomenon is the loss of the direct reaction when covering a blind eye and a friendly response if vision problems are not observed.The reasons most often a variety of diseases of the retina and visual pathway.If unilateral immobility is the result of amaurosis (retinal lesions), and combined with dilated pupils, although small, there is a possibility of anisocoria (pupils are different sizes).In such abuse other pupillary reaction not affected.If amaurosis develops on both sides (that is, both eyes are affected at the same time), the pupils do not react even when exposed to the sun's rays are extended, that is, the pupillary reflex is absent.
- Another type amavroticheskoy immobility of the pupils - gemianopicheskaya immobility of the pupil.Perhaps there is a defeat of the optic tract, which is accompanied by hemianopsia, ie blind half of the visual field, which is expressed by the lack of pupillary reflex in both eyes.
- reflex immobility syndrome or Robertson.It lies in the complete absence of both direct and friendly reaction of pupils.However, unlike the previous species destruction, response to convergence (pupillary constriction in if eyes focus on a specific point) and accommodation (change in external conditions in which there is a person) is not broken.This symptom is caused by the fact that there are changes in parasympathetic innervartsii eyes when there is destruction of parasympathetic nucleus, its fibers.This syndrome may indicate a severe stage of syphilis of the nervous system, rarely informs encephalitis syndrome, brain tumors (namely in the area of the feet), as well as traumatic brain injury.
- absolute or complete immobility of the pupil (ie, it is not shrinking, not expanding at all).When exposed to a beam of light rays pupil diagnosed absence of both direct and friendly reaction to the stimulus.Developing such a reaction is not immediately, but gradually.As a rule, it begins with the violation of physiological pupillary reactions - mydriasis (pupil dilation), the lack of mobility of pupils.
cause may be the inflammatory processes in the core, the spine or trunk of the nerve responsible for eye movements, the focus in the ciliary body tumors, abscesses posterior ciliary nerves.