Why is the light sensitivity of the eyes impaired?

Diagnostic methods

Gynecological medicine is 80% based on endocrinological research.
Therefore, the connecting functions of the reproductive system are based on the analysis of changes in hormonal status and processes caused by hormones in the female body. The amount of hormones is determined by blood and urine tests. To determine ovarian function, functional diagnostic tests are performed: 1. Colpocytological examination. This test is carried out to identify and diagnose problems in the female organs responsible for childbirth. The analysis determines:

• bleeding from the uterus, infertility, and so on;
• the beginning of ovulation.

This study is carried out using a pipette or a special spoon. The material located on the side wall of the vagina is collected with an instrument and placed on the edge of a laboratory glass, making a narrow smear. After collection, the smear is dried and stained.

2. Analysis of the properties of glassy mucus (symptom of the pupil and “fern”) determines:

• viscosity and consistency, which depend on the amount of proteins and ions;
• distensibility reaching 14 cm in the periovulatory period;
• crystallization (the state of mucus after drying on glass).

The secretion and refractive power of cervical secretions change, determining the basis of the phenomena called “fern symptom” and “pupil symptom”. The diagnostic method is based on determining the quantity and quality of mucus in the cervical cavity.

3. Determination of basal temperature. The method allows you to determine the effect of progesterone on the thermoregulation center by increasing the temperature. If the corpus luteum functions normally, body temperature increases in the post-ovulation period.

4. Histological examination of endometrial scraping. Helps determine the causes of infertility, menstrual dysfunction, amenorrhea, and so on.

Pupil response to stimulants

Psychostimulants are drugs that stimulate the nervous system. These include Cocaine, Amphetamine, Ecstasy, LSD, Pervitin, Mephedrone (Salt).

The eyes of a stimulant addict may have dilated pupils for several days. This happens due to severe overexcitation of the sympathetic nervous system. The effect of psychostimulants on the body lasts for 1-2 days, and during this time the pupil does not constrict.

Symptoms of stimulant and opiate drug use are easy to check. They shine a flashlight into the person’s eyes, then sharply turn the beam of light to the side and repeat the procedure. If there is no reaction or it is insignificant, this is a serious symptom of drug addiction.

The eyes of a drug addict

Pathological causes of dilated pupils

The causes of dilated pupils are often symptoms of various diseases. As a rule, these are head injuries or some malfunction of the thyroid gland. When, in addition to dilated pupils, other symptoms of deterioration in well-being appear, for example, increased blood pressure, headaches accompanied by nausea or vomiting, you should immediately seek medical help. Only a specialist will determine the true cause of these symptoms and prescribe appropriate treatment.

The cause of temporary dilation of the pupils can be damage to the central nervous system - stroke or epilepsy.

Injuries to the eyes or head, with damage to the eye muscle, which is responsible for the correct functioning of the pupil, also causes its persistent dilation. In these cases, we are talking about a violation of the process of contraction and expansion. Pupil dilation also occurs under the influence of alcohol, narcotic substances, and psychotropic drugs. If these factors influence the dilation of the pupils, it is necessary to immediately begin treatment: physical and psychological.

Review of root causes

The diameter of the pupil is controlled by the centers of the optic nerve (we are talking about the third pair of cranial nerves). Their nuclei are located inside the brain; in a normal state, they function in harmony. In some cases, there is a mismatch, and for a variety of reasons.

Pupil diameter is normal

More specifically, one pupil may increase in size due to:

• cluster headache or migraine;
• Eydie syndrome in case of infection with ocular herpes or the presence of congenital myotonia (the fact is that the herpes virus can affect not only the pupil, but also the nerves leading to it, which is why the deviation described in the article appears);
• CNS infections;
• endocrine diseases, thyroid carcinoma;
• multiple sclerosis of one optic nerve;
• neck injuries;
• congenital pathologies;
• central nervous system tumors;
• inflammation or injury to the eye (due to injury, the pupillary muscles can be affected, as a result of which the diameter of the eye is no longer regulated as expected);
• drug use;
• reflex in the case of pulmonary tuberculosis (mydriasis of the eye is observed on the side affected by tuberculosis).

Mydriasis (pupil dilation)

Migraine

A common cause of anisocoria is cluster pain. In one hemisphere of the brain, blood circulation is disrupted, which leads to asymmetry of the pupils. In addition, with migraines, blood vessels dilate, pressure inside the skull increases, and brain tissue swells. Migraines are also characterized by the so-called Horner's syndrome, which includes drooping of the eyelid, redness, recession or miosis of the eye on the affected side.

This triad of symptoms is referred to as Horner syndrome (or Claude-Bernard-Horner syndrome)

CNS infections

A number of neuroinfections (for example, encephalitis, meningitis) may be accompanied by impaired functionality of the optic nerve nuclei. In addition, a person’s reflexes increase/weaken, neck stiffness and headaches occur. The patient cannot touch the neck with the chin. But other neurological symptoms may also be observed.

Ways of infection with meningitis

Multiple sclerosis

In cases of multiple sclerosis, scar tissue appears inside the nerve fibers. In this case, the electrical impulse practically does not pass through such tissues, which is why the fibers leading to the eye cease their previous functioning. As a result, the pupils no longer respond properly to changes in lighting.

Multiple sclerosis

Hematomas

Hematomas after injuries can lead to compression of important parts of the brain (for example, the brain stem), which can provoke anisocoria. The same is observed with strokes, which are caused by rupture of blood vessels or thrombosis of the arteries that supply the brain.

Anisocoria is a symptom characterized by different pupil sizes in the right and left eyes

Abscesses, brain cancer

Malignant neoplasms, as they progress, cause swelling and increased pressure inside the skull. In some cases, if the tumors are especially large, wedging of the trunk is observed. If the tumor grows into the vessels, hemorrhages and compression of nearby tissues are also possible.

Brain tumor is one of the most intractable diseases

Drugs, alcohol

Usually, in a person who has consumed alcohol or drugs, both pupils dilate, but in some cases they may dilate unevenly.

Prozerin

As a rule, in case of poisoning, the constriction/dilation of the pupils is simultaneous, but if one eye or the optic nerve is damaged, then, accordingly, the pupil may not respond to the effects of chemicals.

Causes of pain

Some people experience eye pain from sunlight or electric light. The photosensitivity of the retina increases, which occurs as a result of malfunctions in the body. The reasons for the appearance of this pathological phenomenon include:

• prolonged stay in front of a computer or TV;
• taking medications with an adverse reaction - photophobia;
• the result of radioactive exposure.

Also, the eyes hurt in the sun or in a room with bright artificial lighting and watery with the following pathologies and conditions:

• keratitis;
• acute or chronic conjunctivitis;
• iritis;
• myopia;
• glaucoma;
• direct look at the sun;
• bruise and eye injury;
• arterial hypertension;
• headache and migraine;
• reflection from white snow;
• a brain tumor;
• emotional stress;
• entry of a foreign body into the eye area;
• colds;
• encephalitis;
• VSD;
• trigeminal neuralgia;
• stroke;
• the natural aging process of the eye lens;
• albinism;
• brain abscess;
• head injury;
• lack of melanin or its absence;
• inflammation of the iris or cornea of ​​the eye;
• toothache;
• incorrectly selected glasses;
• sinusitis.

Anatomical features of the pupil structure

The pupil looks like a round hole in the central part of the iris. It can change its diameter, adjusting the area of ​​absorption of light rays entering the eye. This opportunity is provided to him by the eye muscles: sphincter and dilator. The sphincter surrounds the pupil, and when it contracts, it narrows. A dilator, on the contrary, expands, connecting not only with the pupillary opening, but also with the iris itself.

The pupillary muscles perform the following functions:

• The diametrical size of the pupil is changed under the influence of light and other stimuli entering the retina.
• The diameter of the pupillary opening is set depending on the distance at which the image is located.
• They converge and diverge on the visual axes of the eyes.

The pupil and surrounding muscles work according to a reflex mechanism that is not associated with mechanical irritation of the eye. Since impulses passing through the nerve endings of the eye are sensitively perceived by the pupil itself, it is capable of reacting to the emotions experienced by a person (fear, anxiety, fright, death). Under the influence of such strong emotional arousal, the pupillary openings dilate. If excitability is low, they narrow.

Human pupil: structure and reactions

The change in its diameter occurs due to the work of two muscle groups: the sphincter and the dilator. The sphincter is located directly around the pupil. This is circular smooth muscle tissue, the contraction of which leads to a decrease in the diameter of the hole. The dilator is a muscle located on the pigment part of the eye (iris) that is responsible for dilatation.

Classification

There are two types of reaction: miosis (constriction) and mydriasis (expansion). The causes can be either natural, functional, or pathological, which indicate serious damage to the body (usually the brain). Dilated pupils at death can also be attributed to physiological causes.

Various types of coma also manifest themselves in constriction or dilation of the pupil. Metabolic coma can be determined by the persistence of the reaction to light, even in the absence of other neurological reflexes. For comparison: in a comatose patient with TBI, the reaction to light is weakened or completely absent. In general, the condition and response to light allows you to determine the area of ​​​​brain damage.

Changing the pupil as a method for diagnosing diseases

A pathological, non-congenital difference in diameter is called anisocoria. It may be a sign of serious disorders in the body:

• optic nerve damage
• cerebral aneurysm,
• traumatic brain injury,
• stroke, hemorrhage.

In addition to diameter and symmetry, assessment of reaction speed, shape and color help in diagnosing diseases (gray color in side lighting signals cataracts).

Reference. According to statistics, 20% of the world's population has pupils of different sizes due to a congenital anomaly.

Why does the pupil not react to light?

Under normal conditions, human pupils react sensitively to light stimuli.

If this does not happen, then the doctor may have many suspicions.

There are a large number of factors that can cause such a pathological process.

This is mainly due to the presence of congenital diseases or previous injuries.

It is important to study the clinical picture in detail, since it has similarities with various ophthalmological diseases. The doctor must prescribe a full examination and then determine treatment options

How pupils should react to light

How pupils should react to light

In most cases, the pupils dilate when exposed to bright light. Any exposure to the eyes may have negative consequences. If there is no reaction to light, you should consult a doctor.

It is important to consider that the pupils may constrict when exposed to too much bright light. Do not forget about the individual characteristics of a person

Everyone's eye structure, reactions and vision may have unusual features.

With certain pathologies, one eye may react to light, but the other does not.

Causes

Causes

When a dilated pupil does not respond to light, it should be a cause for concern. The patient should visit a specialist as soon as possible. Such violations can be associated with many factors:

• injuries to the nerves that are responsible for the mobility of the visual organs;
• visual difference in pupils;
• pupillary sphincter injuries;
• long-term use of certain medications.

In some cases, the pupils contract or dilate under the influence of an emotional state. Given age-related changes, the pupil may not narrow enough. This is due to decreased sensitivity. Doctors often say that narrow pupils are not in all cases a sign of pathology.

This may be due to the influence of such factors:

• insufficient lighting in the room;
• the influence of strong positive or negative emotions;
• scientists say that if a person looks at another with love and sympathy, then mydriasis is observed.

The true cause can only be determined after a thorough examination of the visual organs.

Possible diseases

Possible diseases

Bright light can affect the pupils of each person differently. If the symmetry of the face is correct, then the presence of pathology can be excluded. When sick, a person’s emotions do not have a natural appearance.

It seems that the person is baring his teeth and spreading his lips excessively.

If the body temperature does not rise, the limbs have the usual sensitivity, there is no nausea and vomiting, then there is no pathological process.

Possible diseases:

• Optic nerve damage. In the absence of a reaction to light in the blind eye, a concomitant contraction of the sphincter of the pupil in the other eye is observed.
• Damage to the nerve that is responsible for the mobility of the visual organs. When the third nerve is damaged, there is a lack of direct, indirect and friendly reactions to light.
• Eddie's syndrome. Often causes impaired pupillary response.

If a person observes the development of suspicious symptoms, they should immediately consult a doctor.

Diagnostics

Diagnostics

To identify violations, the doctor conducts various examinations. Visual inspection:

• determination of pupil reaction to light;
• identification of accommodative abilities;
• assessment of peripheral and central vision.

Additional examinations:

• biomicroscopy to study the condition of the lens and the passage of light through it;
• ophthalmoscopy to examine the fundus and other structures;
• assessment of the condition of the iris;
• laboratory tests of blood, feces, urine;
• CT and MRI if internal pathologies are suspected.

After the examination results, the doctor can determine the treatment method.

My eyes hurt from the light and my head hurts

Eye pain and headache often accompany each other. The pain can “originate” first in the eye area and gradually move to the head, or it can arise somewhere in the back of the head and slowly spread to the organs of vision.

Doctors identify several diseases that cause these symptoms:

• Myopia (myopia) - severe tension in the eye muscles provokes a painful reaction of the nerves located in the head. Perhaps the diopters for your glasses were chosen incorrectly.
• Overfatigue - your eyes are constantly strained when you work for a long time at the computer, relax in front of the TV, or are mentally overstrained at work. This negatively affects the condition of the optic nerve, especially in a child who sits in front of a monitor for too long. The pain usually appears in both eyes in the afternoon.
• High blood pressure - eye pain with high blood pressure and visual disturbances, including light sensitivity.
• Head injuries - a sign of a concussion is headaches, which are reflected by pain in the eyes.
• Infectious lesion of the brain - pain is localized in the temples and eyes, moving to the occipital region. Additionally, dizziness, nausea, and weakness occur, which indicates symptoms of meningitis. The sooner you see a doctor, the lower the risk of death.
• Colds and flu are accompanied by pressing pain in the head and increased sensitivity to light.
• Migraine - occurs due to emotional and physical overload, weather changes, consumption of chocolate, cheese, nuts. The body begins to react in the form of throbbing pain in the temple area.
• Glaucoma - when the flow of fluid inside the eye is impaired, intraocular pressure increases. The disease is characterized not only by headache and eye pain. Patients often say: “I can’t look at the light, there’s something pressing on my eyes,” a colored halo appears around the light bulbs. If glaucoma is not diagnosed in time, the disease will lead to blindness.

In some cases, the eyes hurt from light and the head hurts due to a brain tumor, arteritis, Horton's syndrome, and trigeminal neuralgia.

Also, painful sensations in the eye and head area may indicate disturbances in the blood supply to the tissues around the eyes, when nutrients stop flowing to the visual organs due to vascular diseases. Pain in the eyes is sometimes provoked by disruptions of the vegetative-vascular system, sinusitis and sinusitis.

To determine the name of the disease, consult a specialist. The doctor will conduct the necessary diagnostics and prescribe appropriate treatment.

What should be the normal pupil size?

The pupil in its normal state is a black round dot (however, in albinos its color is red).

Reference! Under normal lighting, which is considered to be daytime room lighting without drawn curtains and switched on lamps, its size, depending on the age and physiological characteristics of different people, ranges from 2 to 6 millimeters.

In dark conditions, to better capture light rays, the pupil can increase to a size of 4-8 millimeters.

The difference between the sizes of the pupils of both human eyes can be up to one millimeter.

But at the same time, the narrowing, depending on changes in lighting conditions, still occurs evenly and simultaneously.

When the size of the pupil changes, a person has absolutely no sensation that such transformations are occurring.

Video

Constriction of the pupils in ophthalmology is called miosis.

This condition can be pathological, but sometimes narrow pupils can also appear in healthy people without any visual impairment.

In a normal state, a person’s pupil does not remain the same size throughout the day, and during the day it can expand and contract several dozen times.

But it is necessary to determine when this occurs for natural reasons and when it is a pathological disorder.

Most dangerous condition

The danger lies in the fact that when the main organ of the central nervous system “gets stuck” with any part in a large opening of the skull, the blood vessels are compressed

As a result, this part dies off, and if it is very large or vital, then the person dies

Symptoms that indicate that any delay could result in disaster include:

• Severe and persistent headaches. In some cases, they torment the patient day and night,
• Apathy and depression. A person becomes like a bear that they are trying to wake up during winter hibernation. He slowly wakes up, consciousness returns gradually, does not understand the questions that are asked to him and cannot give a clear answer to them,
• The head is tilted to one side, all attempts to straighten its position end in failure. In case of serious complications, there is a disruption in the respiratory rhythm,
• Movements of the arms and legs are limited, and the sensitivity threshold is reduced to almost zero. The patient does not perceive any stimuli.

The pupil does not react to light

If patients do not have an eye reaction to a light stimulus, a number of questions arise.

First of all, you should understand the causes of the manifestation, which may relate to congenital diseases or traumatic injury.

Doctors note that symptoms can be confused with serious diseases. A diagnosis of the optic nerves is prescribed, and then complex treatment is applied to eliminate the causes of the occurrence.

The pupil dilates due to injuries, in particular cranial injuries, as a result of taking drugs, alcohol, as well as due to eye diseases, chronic pathologies of other organs and systems.

Causes of pathology

When patients are faced with the problem of lack of reaction of the pupils to changes in ambient light, this is a reason to urgently contact a specialist. Such manifestations may occur primarily due to the following reasons:

• injured nerve, which is responsible for the movement of the visual organs;
• disruption of the structure of the ciliary ganglion, which is visualized as different pupils;
• injuries to the sphincter of the eye pupil;
• influence of long-term course of medications.

Constriction of the pupils can be caused by an attack of fear.

The pupil does not narrow sufficiently due to age-related characteristics. This is due in part to a loss of sensation. Doctors also say that narrow pupils of the eye do not always signal the development of the disease. This happens when exposed to the following factors:

• low lighting, in which the visual organs do not need protection from excess light;
• when a person experiences strong emotions: fear, panic or anger;
• when the patient looks with love or strong sympathy, during which the sympathetic nervous system is activated and provokes mydriasis.

How to distinguish from a disease: manifestations

Pay attention to the fact that when exposed to bright light, the pupil quickly becomes narrow and small from a wide one. The absence of disease is indicated by correct facial symmetry when emotions appear.

Usually in such cases, against the background of pathologies, when smiling, it feels like the person is baring his teeth, puffing out his cheeks, or spreading his lips too wide. With physiological mydriasis, no pain should be felt, and there should be no mucus or pus discharge from the eyes.

Body temperature is normal, normal sensitivity in the extremities, absence of nausea and vomiting - this indicates that there is no pathology.

Patients in a coma have dilated pupils.

An unnaturally wide pupil and the absence of other signs of life may indicate clinical or biological death. But there are a number of differences that are presented in the table:

When the pupils are dilated unevenly, they speak of anisocoria, which manifests itself as a result of diseases of the nervous system, osteochondrosis of the cervicothoracic zone, pulmonary tuberculosis, pleurisy, and aortic pathologies. It can occur in healthy people, then the characteristic difference is that the left eye is narrower than the right.

Diagnosis

The doctor begins the examination by checking the response to light exposure.

To determine the causes of mydriasis, the following studies are carried out:

• External examination: checking reaction to light;
• study of accommodation properties;
• analysis of peripheral and central vision.

How to treat?

The fight against a pupil that does not respond to light depends on the cause of the pathology. If the disease appears due to a violation of the structures of the muscle tissue of the eye, a number of gymnastic exercises are prescribed.

This therapy focuses on enhancing vision and restoring correct reactions. When the cause is injury, they first deal with the general condition of the head, and then carry out preventative care for the eyes.

In case of a congenital disorder, individually selected drugs are prescribed depending on the causes of development.

How to treat?

The fight against a pupil that does not respond to light depends on the cause of the pathology. If the disease appears due to a violation of the structures of the muscle tissue of the eye, a number of gymnastic exercises are prescribed. This therapy focuses on enhancing vision and restoring correct reactions. When the cause is injury, they first deal with the general condition of the head, and then carry out preventative care for the eyes. In case of a congenital disorder, individually selected drugs are prescribed depending on the causes of development.

Treatment Options

Treatment depends on what caused the problems.

If miosis occurs as a result of instillation of certain ophthalmic drugs (some of them have such a side effect), mydriatic drugs (midrum, cyclomed, phenylephrine, irifren) can be used to dilate the pupils.

But they should be used only after consultation with an ophthalmologist, and this is not always necessary.

If this phenomenon does not cause any painful or uncomfortable sensations, it is better to wait until the normal state of the pupils is restored on its own.

In case of miosis of pathological origin, it is necessary first of all to undergo examination by an ophthalmologist, who, depending on the causes, will prescribe further treatment from other specialists.

Stay up to date! For diseases of the nervous system and brain, treatment is carried out by a neurologist, and if the problem lies in dysfunction of the thyroid gland, this is the work of endocrinologists.

Diseases with similar symptoms

Even if you see overly dilated or constricted pupils, do not draw hasty conclusions - this may be a symptom of serious diseases.

Pupil dilation may be a sign of:

• Compression or damage to the optic nerve.
• Traumatic brain or eye injury.
• High intracranial pressure.
• Inflammation of the brain (encephalitis).
• Infection with botulism toxin.

Constriction of the pupil may be a sign of:

• Meningitis is inflammation of the meninges.
• Iridocyclitis is inflammation of the iris of the eye.
• Horner's syndrome is a disorder of the sympathetic nerves that impairs the functioning of the eye muscles.

If a loved one looks surprised and frightened by the abnormal reaction of his eyes, does not try to hide it and does not behave aggressively, an urgent need to call doctors.

Do you trust doctors and their prescriptions?

Yes

20.18%

No

12.72%

I trust, but I check all medications for reviews on the Internet from people who have already tried them and only then do I start taking them.

49.56%

Yes, but only to appointments and doctors from paid clinics.

17.54%

Voted: 228

Is there a drug addict in your family? Leave your phone number and our specialists will help you!

What is a thorn

Leukoma (sore) of the cornea of ​​the eye is scar regenerated connective tissue, which is formed during the healing process of all kinds of damage to the cornea. In essence, a thorn is a scar. The pathology can affect one or both eyes at once. Since epithelial cells and protein structures participate in regeneration, the spot becomes opaque, unlike corneal cells.

Due to the appearance of leukoma, it happens:

1. Congenital - a child is immediately born with an eyesore that forms in the womb.
2. Acquired - appears during life under the influence of various factors on the body or cornea.
3. Age-related - aging of tissues and cells of the cornea in old age can provoke corneal dystrophy, the final result of which is a cataract.

Based on the volume of space occupied, leukoma can be:

1. With a central location - the spot covers the most convex part of the cornea, while blocking the pupil. This form is often confused with cataracts.
2. Peripheral location is the initial stage of the disease, which may be subtle and cause virtually no discomfort to the patient.
3. Total, continuous cataract - occurs with significant, deep damage to the cornea, with the risk of compromising the integrity of the orbit.

By severity:

1. Mild degree - translucent, barely noticeable spots, imperceptible to the patient.
2. Medium degree - the spots are visually noticeable, compacted, and have a distinct white color.
3. Severe degree - vascularized corneal cataract, the process of germination of the spot by the vascular network. The cornea itself does not have vessels, but is nourished by microelements found in the intraocular fluid, this ensures its transparency. The epithelial cells from which the cataract is formed do not have this ability, so they actively develop their vascular network, which is clearly visible against the background of the white spot.

Complications of leukoma:

• impaired visual acuity due to the spot leads to strabismus, loss of binocular vision, optic nerve atrophy, amblyopia, and complete blindness;
• scarring of deep lesions can lead to cataracts or blockage of the outflow of intraocular fluid in the anterior chamber and glaucoma (chronic and acute attack);
• the addition of inflammation can contribute to the degeneration of leukoma into oncology and removal of the eyeball.

How to distinguish leukoma from cataracts

The clinical picture of a centrally located leukoma, before vascularization, is very similar to a cataract. The main distinguishing feature of these two pathological processes is the clear visibility of the iris. With cataracts, the lens becomes cloudy, and it is located behind the iris, so it is clearly visible. The thorn affects the upper layer of the eye; neither the iris, nor the pupil, nor the lens are visible through it.

Norm or pathology

Short-term discomfort when the light changes is considered normal. It passes within a few seconds - but can last up to 1.5-2 minutes.

With colds and infectious diseases - especially those accompanied by fever - the adaptation time increases. In addition, bright light begins to irritate, you have to squint your eyes even on a normal sunny day.

You can increase the sensitivity of your eyes yourself if you constantly use sunglasses in the summer. Then the bright light in the room will also begin to irritate.

The following factors affect light sensitivity:

• some medications - as soon as their effect wears off, light perception returns to normal;
• age-related changes;
• visual impairment due to eye diseases - macular degeneration and glaucoma.

Any deterioration in vision is a reason to consult a doctor. Stopping the development of glaucoma is possible only at the initial stage of the disease.

However, it is considered normal if lacrimation increases on a clear winter day. After a short attack of snow ophthalmia, vision is restored quickly. If snowy expanses have to be observed with unprotected eyes for a long time, restoration of vision may take several days.

But again, the body is able to cope with this condition on its own, just take care of the eyes and avoid bright light.

What is light and color sensitivity?

The human eye is not an optimal analyzer. To evoke the sensation of light, 2 colors are perceived at once - if the perception is disturbed, then discomfort occurs.

Solar radiation is the maximum of the visibility curve; it is to this that the human eye is tuned.

In the organ of vision - in its retina - there are sensitive elements: optic nerve fibers and photoreceptors. When exposed to electromagnetic radiation in the range from 760 to 380 nm, a sensation of light arises. Light-sensitive receptors face deep into the retina, the outer shell of which consists of epithelial cells with black pigment.

An excitation impulse appears in the cells under the influence of light, causing photochemical reactions in them. The impulses provoked by this process are transmitted to the brain, as a result of which visual sensations are formed.

Under the influence of light, the retina evaluates the surroundings according to two characteristics - qualitative and quantitative. A quantitative characteristic is a feeling of brightness, a qualitative characteristic is a feeling of color. Perception is determined by the wavelength of light and spectral composition.

Photoreceptors are divided into rods and cones. Rods are more photosensitive; they are responsible for brightness, while cones distinguish colors and shades.

The graph, relative to which you can approximately understand how the color and light sensitivity of the eyes is distributed, looks like this.

This picture shows that the perception of bright light and contrast for a person is a mixture of red, green and blue. Increasing the photosensitivity of the eyes is a change in the proportions between the analyzers located in the organ of vision - with artificial enhancement of one of the spectra, painful sensations appear.

It is impossible to depict the photosensitivity of the eyes with a picture; there are very complex formulas; the emission spectrum is estimated using optical formulas.

The reciprocal of the minimum threshold brightness that causes visual sensations is called the photosensitivity of the eye.

The range of its changes is quite wide, which is why the human eye has enormous visual adaptation capabilities - the ability to adapt to light of varying brightness.

During adaptation the following happens:

1. The diameter of the pupil varies, which allows you to change the perception of light flux;
2. Inside the organ of vision, the concentration of photosensitivity of undecomposed pigment decreases;
3. Cones and rods with dark pigment, which are located in the choroid, move towards the vitreous body and screen the image;
4. Depending on the brightness of the object, the degree of participation of rods and cones in exciting the sensation of light changes.

When performing an eye photosensitivity test, the test subject is placed in a dark room. Under these conditions, photosensitivity is determined - how transitions from the lower limit to the upper limit and vice versa affect the organ of vision.

The absolute threshold of susceptibility or the lower limit is only a few tens of photons per second - such a flow of energy is directed at the organ of vision in almost complete darkness. The upper limit is 1012 times higher. Adaptation should take less than a minute for young people; in old age, its time may increase.

Increased photosensitivity

The following reasons cause increased photosensitivity:

• congenital absence of pigment;
• staying at the computer for a long time – eye fatigue;
• retinal disinsertion;
• eye diseases - iritis, keratitis, ulcers and damage to the cornea, tumors.

Photophobia occurs after the eyes are damaged by bright light - for example, during welding work or with snow ophthalmia.

Also, discomfort from intense light appears during many diseases that occur with high temperature. One of the symptoms of childhood diseases - measles and scarlet fever - is an increased reaction to light.

Symptoms of increased photosensitivity may include:

• increased lacrimation;
• pain and pain in the organ of vision;
• spasms causing convulsive closure of the eyelids.

A sharp change in illumination provokes an attack of acute headache.