If you close your eyes for just a minute and try to live in complete darkness, you begin to understand how important vision is for a person. How helpless people become when they lose the ability to see. And if the eyes are the mirror of the soul, then the pupil is our window to the world.
The structure of the eye
The human organ of vision is a complex optical system. Its main purpose is to transmit an image through the optic nerve to the brain.
The eyeball, which has the shape of a sphere, is located in the orbit and has three shells: fibrous, vascular and retina. Inside it are aqueous humor, lens and vitreous body.
The white segment of the eyeball is covered with a mucous membrane (sclera). The front transparent part, called the cornea, is an optical lens with a large refractive power. Below it is the iris, which acts as a diaphragm.
The stream of light reflected from the surfaces of objects first hits the cornea and, refracted,enters through the pupil to the lens, which is also a biconvex lens and enters the optical system of the eye.
The next point on the path of a human-visible image is the retina. It is a shell of cells that are sensitive to light: cones and rods. The retina covers the inner surface of the eye and transmits information to the brain via nerve fibers through the optic nerve. It is in him that the final perception and awareness of what he saw takes place.
Pupil function
There is a phraseologism popular among the people: “cherish like the apple of an eye”, but few people today know that the pupil was called the pupil in the old days. This expression has been used for a long time and is the best way to show how we should treat our eyes - as the most valuable and expensive.
The human pupil is regulated by two muscles: the sphincter and the dilator. They are controlled by different groups of nerves related to the sympathetic and parasympathetic systems.
The pupil is, in fact, the hole through which light enters the retina of the eye. It acts as a regulator, shrinking in bright light and expanding in low light. Thus, the pupil of the eye protects the retina from burns and increases visual acuity.
Mydriasis
Is it normal for a person to have a dilated pupil? It depends on a number of factors. In the medical community, this phenomenon is called mydriasis.
It turns out that pupils react not only to light. Their expansion can be provoked by excitedemotional state: strong interest (including of a sexual nature), violent joy, unbearable pain, or fear.
The above factors cause natural mydriasis, which does not affect visual acuity and eye he alth. As a rule, such a state of the pupil passes quickly if the emotional background returns to normal.
The phenomenon of mydriasis is typical for a person who is intoxicated with alcohol or drugs. In addition, dilated pupils often indicate a serious poisoning, such as botulism.
Pathological mydriasis can often be observed in patients with traumatic brain injury. Constantly dilated pupils indicate that a person has a number of possible diseases:
- glaucoma;
- migraines;
- oculomotor nerve palsy;
- encephalopathy;
- thyroid dysfunction;
- Eddie syndrome.
Many people know from films that when you faint, first aid doctors examine the eyes. The reaction of the pupils to light, as well as their size, can tell doctors a lot. A slight increase indicates a shallow loss of consciousness, while "glassy", almost black eyes signal a very serious condition.
Miosis
Disproportionately constricted pupil is the reverse of mydriasis. Ophthalmologists call it miosis. Such a deviation also has a number of reasons, it can be a harmless visual defect, but often this is a reason to immediately turn todoctor.
Specialists distinguish between several types of miosis:
- Functional, in which narrowing occurs due to natural causes, such as poor lighting, sleep conditions, infancy or old age, farsightedness, overwork.
- Medication miosis is the result of taking drugs that, in addition to the main function, have an effect on the work of the eye muscles.
- Paralytic - characterized by a complete or partial absence of the motor ability of the dilator.
- Miosis of irritation - observed with spasm of the sphincter. Common in brain tumors, meningitis, encephalitis, and in people with multiple sclerosis and epilepsy.
- Syphilitic miosis - can manifest itself at any stage of the disease, although it rarely develops with timely therapy.
Anisocoria
According to statistics, every fifth person on Earth has pupils of different sizes. This asymmetry is called anisocoria. In most cases, the differences are negligible and visible only to an ophthalmologist, but in some, this difference is visible to the naked eye. The regulation of the pupil diameter with this feature occurs asynchronously, and in some cases the size changes only in one eye, while the other remains motionless.
Anisocoria can be either hereditary or acquired. In the first case, this structure of the eye is due to genetics, in the second - by trauma or some kind of disease.
Pupils of different diameters are found in people suffering from such ailments:
- optic nerve damage;
- aneurysm;
- brain injury;
- tumors;
- neurological diseases.
Polycoria
Double pupil is the rarest type of eye anomaly. This congenital effect, called polycoria, is characterized by the presence of two or more pupils in the same iris.
There are two types of this pathology: false and true. The false option implies that the pupil is closed unevenly by the membrane, and it seems that there are several holes. In this case, the reaction to light is present in only one.
True polycoria is associated with the pathology of the development of the eye cup. The shape of the pupils is not always round, there are holes in the form of an oval, a drop, a keyhole. A reaction to light, though not pronounced, is in each of them.
People with this pathology feel significant discomfort, the defective eye sees much worse than normal. If the number of pupils is more than 3, and they are large enough (2 mm or more), a child under one year old is likely to undergo surgery. Adults are prescribed to wear corrective contact lenses.
Age features
Many young mothers often notice that the child's pupils are dilated. Is it worth raising a panic because of this? Isolated cases are not dangerous, they can be caused by poor lighting in the room and features of the excitable nervous system. Seeing a beautiful toy or being afraid of a terribleBarmaleya, the child will reflexively expand the pupils, which will soon return to normal again.
If this condition is observed constantly - this is a reason to sound the alarm and urgently consult a doctor. This may indicate diseases of a neurological nature, and an extra consultation with a specialist will definitely not hurt.
Pupillary response to light changes with age. Adolescents experience the maximum possible expansion, unlike the elderly, for whom constantly constricted pupils are a variant of the norm.
