If you just close your eyes for a minute and try to live in complete darkness, you begin to understand how important vision is for a person. How helpless people become who have lost the ability to see. And if the eyes are a mirror of the soul, then the pupil is our window to the world.
Eye structure
The human organ of vision is a complex optical system. Its main purpose is to transmit the 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 membranes: fibrous, vascular and the retina. Inside it are aqueous humor, the lens and the vitreous.
The white segment of the eyeball is covered with mucous membrane (sclera). The anterior transparent portion, called the cornea, is an optical lens with great refractive power. Under it is the iris, which performs the function of the diaphragm.
The stream of light reflected from the surfaces of objects first hits the cornea and, being refracted, enters through the pupil onto 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 light-sensitive cells: cones and rods. The retina covers the inner surface of the eye and through nerve fibers through the optic nerve transmits information to the brain. It is in it that the final perception and awareness of what is seen occurs.
Pupil function
There is a popular phraseology: “take care like the apple of an eye”, but few people today know that the pupil was called the apple in the old days. This expression has been used a long time ago and shows us in the best way how we should relate to our eyes - as the most valuable and dearest.
The human pupil is regulated by two muscles: the sphincter and the dilator. They are controlled by various groups of nerves belonging to the sympathetic and parasympathetic systems.
The pupil is, in fact, the hole through which light enters the retina . It acts as a regulator, tapering in bright light and expanding with its lack. Thus, the pupil of the eye protects the retina from burns and increases visual acuity.
Mydriasis
Is it considered normal when a person has a dilated pupil? It depends on a number of factors. In the medical environment, this phenomenon is called mydriasis.
It turns out that pupils react not only to light. Their expansion can be triggered by an excited emotional state: strong interest (including sexual nature), violent joy, unbearable pain or fear.
The factors listed above cause natural mydriasis, which does not affect visual acuity and eye health. As a rule, such a state of the pupil passes quickly if the emotional background returns to normal.
The phenomenon of mydriasis is characteristic of a person who is intoxicated or intoxicated. In addition, dilated pupils often indicate serious poisoning, for example, butulism.
Pathological mydriasis can often be observed in patients with traumatic brain injury. Constantly dilated pupils indicate the presence of a number of possible diseases in a person:
- glaucoma
- migraine;
- paralysis of the oculomotor nerve ;
- encephalopathy;
- thyroid dysfunction;
- Eddie's syndrome.
Many people know from films that when fainting, emergency doctors first examine the eyes. The reaction of the pupils to the light, as well as their size, can tell doctors a lot. A slight increase indicates a shallow loss of consciousness, while the "glass", almost black eyes signal a very serious condition.
Myosis
An excessively narrowed pupil is a condition opposite to mydriasis. Ophthalmologists call it myosis. Such a deviation also has a number of reasons, it can be a harmless visual defect, but often this is an occasion to immediately consult a doctor.
Specialists distinguish several types of miosis:
- Functional, in which the narrowing occurs for natural reasons, such as poor lighting, sleep conditions, infancy or senility, hyperopia, overwork.
- Medical 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 lack of motor ability of the dilator.
- Myosis of irritation - observed with spasm of the sphincter. Often found in tumors in the brain, meningitis, encephalitis, as well as in people suffering from multiple sclerosis and epilepsy.
- Syphilitic miosis - can occur at any stage of the disease, although with timely treatment it develops extremely rarely.
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 noticeable only to the ophthalmologist, however, for some, this difference is visible to the naked eye. The regulation of the diameter of the pupils with this feature occurs asynchronously, and in some cases the size changes only in one eye, while the other remains motionless.
Anisocoria can be both hereditary and acquired. In the first case, such an eye structure is due to genetics, in the second - due to trauma or some kind of disease.
Pupils of different diameters are found in people suffering from such ailments:
- damage to the optic nerve;
- aneurysm;
- brain injuries;
- tumors;
- neurological diseases.
Policory
The double pupil is the rarest type of eye anomaly. This innate 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 version implies that the pupil is not uniformly closed 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 pathology of the development of the optic goblet. The shape of the pupils is not always round, there are holes in the form of an oval, a drop, a keyhole. The reaction to light, albeit not pronounced, is in each of them.
People with such a pathology feel significant discomfort, a 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 will most likely have surgery. Adults are prescribed wearing contact lenses.
Age features
Many young mothers often notice that the child has dilated pupils. Is it worth it to raise a panic because of this? Isolated cases are not dangerous, they can be caused by poor illumination in the room and features of the excitable nervous system. Seeing a beautiful toy or frightened by the terrible Barmaley, the child will reflexively dilate the pupils, which will soon return to normal again.
If this condition is constantly observed - this is an occasion 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 certainly not hurt.
The reaction of pupils to light changes with age. In adolescents, the maximum possible expansion is observed, in contrast to the elderly, for whom constantly narrowed pupils are the norm option.