Upon careful examination of the iris, you can clearly see its structure. The iris at its highest point has a ruff, designated by the term “Krause’s circle.” This circle divides the iris into two parts - the outer ciliary and less voluminous - the inner pupil.
The iris on its surface on both sides of the mesentery has slit-like grooves, which are also referred to as lacunae or crypts. The thickness of the iris can be from 0.2 to 0.4 mm. The thickest layer of the iris is located at the pupillary edge; along the periphery this layer is narrower.
Basic functions and color of the iris
The width of the light stream that penetrates through the pupil to the retina depends on the functioning of the iris of the eye. The iris, or rather its muscle layer, has a dilator - a muscle that is responsible for dilating the pupil. There is also the opposite muscle - the sphincter, its structure and work allows the pupil to narrow.
Thanks to these muscles, illumination is always maintained at the required level. The most minimal lighting leads to dilation of the pupil, and this, in turn, increases the flow of light passing through the pupil. Bright lighting causes the pupil size to contract and the flow of incoming light decreases. The work of the dilator and sphincter also depends on the emotional state, taking certain groups of medications, and pain.
In the photo, the iris of the eye looks like an opaque layer. The color of the iris depends on the melanin pigment found in it; usually its concentration is inherited.
In children, the iris is usually blue for the first six months of life and only then changes color. This is explained by weak pigmentation at birth; as they grow older, the number of cells containing pigment increases significantly.
In rare cases, the iris may contain no melanin at all. The absence of pigments is observed not only in the iris, but also in the skin and hair follicles. People with this pathology are called albinos, and each of us has seen them (if not in life, then in photos or in movies). Even less common is the phenomenon of heterochromia, that is, different colors of the iris in both eyes in one person.
Methods for diagnosing iris diseases
Several methods are used to identify iris pathologies. The simplest ophthalmological procedures include external examination and examination using a microscope. It is also not difficult to measure the external diameter of the pupil. The vascular wall of the iris is examined using fluorescein angiography.
All these studies help to determine whether the iris has developmental anomalies - heterochromia, albinism, pupillary dislocation. Also, these methods help to identify diseases and damage to the iris, which allows you to prescribe a course of therapy appropriate to the identified pathology. The most common diseases of the iris include inflammatory processes.
Symptoms of iris diseases
Inflammatory processes of the iris in ophthalmology are usually referred to by the general term “iritis”. If the ciliary body becomes inflamed, the disease is called “iridocyclitis.” When inflammation spreads to the entire choroid, the disease is already called “uveitis.”
The iris can become inflamed under the influence of not only external negative factors. Microorganisms in the blood can also cause pathological changes: bacteria, fungi, helminths, viruses, and allergens.
The iris of the eye is very often affected by active rheumatism, ankylosing spondylitis, inflammation of large and small joints, herpes, diabetes, tuberculosis, and syphilis. Inflammation of the iris can be caused by a burn or injury. There are several symptoms indicating damage to the iris:
- severe pain, usually in one eye;
- lacrimation, photophobia;
- headache, worse in the evening and at night;
- loss of previous clarity of vision;
- blue-red tint of the eyeball, clearly visible during external examination (the iris itself may change its color to green or gray-brown);
- changes in structure, deformation of the pupil.
All these signs allow the doctor to make the correct diagnosis.
Treatment of iris diseases
Lack of competent and timely treatment of diseases and lesions of the iris can lead to complete loss of vision or further damage to the retina and choroid. In case of inflammation of the iris, inpatient treatment is usually prescribed, as this allows the doctor to constantly monitor the condition of the eye and, if necessary, adjust therapy. For local inflammation, the ophthalmologist prescribes various drops and ointments with anti-inflammatory components, mydriatics and corticosteroids.
It is necessary to remember that independent choice of drugs can lead to irreparable consequences, including complete blindness. Before visiting an ophthalmologist, you can only take analgesics for severe pain.
At first glance, the iris of the eye appears to be an ordinary colored disk that occupies a significant part of the eyeball. But in fact, it is a real diaphragm that lets into the eye exactly the amount of light that is necessary for a person to see normally. Therefore, the iris is a complex part of the eyeball, which consists of many connective tissues and muscles.
The eyes are the most important tool available to humans. They not only provide correct orientation in space, but also give a sense of perspective and color. Conventionally, the eyes consist of five main parts, and one of them is the iris.
The iris is located at the front of the eyeball, between the lens and the cornea. This is the most visible part of the eye because it is colored a certain way. It is responsible for ensuring that exactly the amount of light that is necessary for normal vision enters the eye, just like the hole in a photo or video camera does.
In the middle of the iris there is a round black hole called the pupil. Its size can vary depending on how the small muscles of the iris act. They can either expand or contract the black pupil. When the sphincter muscles are relaxed, the pupil dilates, allowing more light to enter the eye and reach the retina. When the muscles tense, the pupil constricts and the number of light rays focused on the retina decreases.
The contraction and dilation of the pupil depends on the lighting. At night, for example, the muscles make the pupil wide so that enough light can enter the eye. If there is too much bright light around, the pupil narrows and lets in less light to prevent damage to the retina. The iris also serves as a barrier that separates the anterior chamber of the eye from the posterior chamber. The posterior chamber is located between the iris and the lens, and the anterior chamber is located between the cornea and the iris.
Iris defects
In some cases, a person may have a defective or damaged iris. When this happens, it cannot function normally, which affects a person's vision. If the damage is small, a person may have small holes in the iris that allow additional rays of light to enter the retina. This causes a phenomenon called ghost shadows or double images. When this happens, it can be very difficult for a person to focus on a subject.
Any part of the iris or eye where it is located, including the uvea and retina, can become diseased or infected. These may be diseases such as:
- Iritis is an inflammatory process in the tissues of the iris, leading to blurred vision and increased sensitivity to light.
- Iridocyclitis - affects the iris and ciliary muscle. Although both of these symptoms can be successfully treated with antibiotics, it is important to start treatment early in the disease. If this is not done, vision deterioration and even irreversible blindness may occur.
- Aniridia is a congenital eye disease when the iris is underdeveloped or there is an absence of the iris (there are only rudiments of a ring). This disease is caused by a genetic defect that begins to appear in the fetus in the womb.
- Coloboma of the iris - can occur either due to an accident or a genetic defect. With this disease, a hole appears in the iris, causing the pupil to take an unusual shape.
Iris diseases can also include injuries resulting from accidents. Sometimes the iris is damaged by puncture wounds from sharp objects, a blow to the eye, or fireworks.
Is it possible to predict the color of a child's eyes?
While the tissues in the iris are involved in controlling the amount of light rays incoming, the pigments contained in the iris are responsible for the color of a person's eyes. The more of it there is in the iris, the darker the color will be. Therefore, blue eyes have the least amount of melanin, and dark brown eyes have the most. Each person has a unique iris in terms of pattern and texture, so the iris can be accurately identified as a fingerprint.
Eye color is a hereditary trait. What a child's eyes will look like depends on the genetic material each parent contributes. But genes can mix in unpredictable ways, so the influence of each parent is unknown until the very moment the child is born.
Human eye color depends on three genes, two of which have been well studied. These genes are responsible for the appearance of colors such as green, dark brown and blue. The genes that are responsible for other colors (gray, olive and various combinations) have not been studied enough and are poorly explained at present.
Although dark brown is considered dominant and blue is recessive, modern research shows that not everything is so simple. In addition, scientists have determined that the color of a child's eyes is not a mixture of the eye colors of the parents, but chromosomes are directly involved, each of which contains two pairs of genes, which determine hereditary traits. Each normal cell in the human body usually contains 23 pairs of chromosomes. Therefore, there are 46 of them in total, half of which are inherited from the mother, and the other half from the father.
Therefore, there are an innumerable number of possible combinations, and predicting them with modern equipment is not easy. Thus, several years ago, Dutch researchers reported that they had developed DNA analysis methods that make it possible to determine with 90% probability whether a child will have dark brown or blue eyes. In May 2010, they admitted that these DNA studies had failed.
It is worth noting that in children, the eye color of their parents may be absent and be completely different. But if the father and mother have dark brown eyes, then there is a high probability that their child will also have dark brown eyes. At the same time, darker colors usually dominate, so often dark brown wins over green, and green beats blue. But a mother's blue eyes and a father's dark brown eyes will not necessarily lead to the birth of a brown-eyed child.
Why does the color of the iris change?
Most newborn babies have blue eyes, which darken during the first three years of life. Darkening of the iris occurs because melanin, a dark brown pigment, is not present in the body at birth and appears only over time.
The iris changes in size during the dilation and constriction of the pupil. This causes the distribution of pigment in the iris to change, causing the eye color to change slightly. That is, in the dark it becomes richer, and when reading it brightens a little.
The size of the pupil and the color of the iris can change as a result of certain feelings and emotions. Therefore, it is not without reason that people say that changes in eye color are influenced by anger and love.
Age is another reason for changes in the color of the iris. This happens to 10-15% of the world's white population (Indo-Europeans have lighter eye color compared to other races). For example, olive color may darken over time.
Although changes in eye shade are considered a normal process, you need to be wary if an adult’s eye color changes dramatically. For example, one eye will change color from dark brown to green or from blue to dark brown (heterochromia). If this happens, you should definitely consult a doctor. This may be a symptom of serious diseases, including heterochromic iridocyclitis, pigmentary glaucoma, Horner's syndrome (damage to the sympathetic nervous system).
When it comes to children, some babies are born with irises that are different colors in each eye. This is usually the result of improper delivery of pigment to the eye tissue, injury during pregnancy or immediately after birth. Sometimes the cause may be hereditary mutations. Other causes include inflammation, moles on the iris, and Horner's syndrome.
In general, heterochromia (meaning different colors) is not a disease in itself. Doctors use this medical term to describe the condition of multi-colored eyes. Other terms that describe this phenomenon are heterochromia iridis and heterochromia iridium. They represent different colors of the iris. However, we are not always talking about different-colored eyes. Sometimes within the same iris you can see a transition of colors, for example, from brown to gray.
Heterochromia is not a disease and does not affect visual acuity, although it can be a symptom of an illness. Benign heterochromia can give a person a fascinating and even exotic appearance. There are many examples of charismatic personalities and actors with eyes of different colors.
Heterochromia also occurs in animals. For example, multi-colored eyes can be seen in dog breeds such as Siberian Husky, Collie, Australian Shepherd, and Chihuahua. Heterochromia also occurs in cats, especially often in representatives of breeds such as the Turkish Van, Turkish Angora, Japanese Bobtail, and Sphynx.
The iris is an automatic diaphragm that divides the space between the cornea and the lens.
It is formed by the most anterior part of the choroid, which is accessible for inspection in humans without the use of any aids.
However, the iris does not completely separate the anterior chamber from the posterior segment of the eye, since in its center there is a hole - the pupil, which has a variable diameter. In physical and optical terms, the iris can be compared to the diaphragm of a camera. It regulates the amount of light passing through the pupil to the retina, maintaining it at a certain level.
This is possible thanks to the coordinated work of specialized muscles - the sphincter and dilator. In low light, the pupil dilates and lets in more photons of light. In bright light, the pupil aperture contracts sharply, and this prevents the eye from being blinded by an excess flux of photons.
In addition, by constricting the pupil, spherical and chromatic aberrations are eliminated and depth of field is maintained on the retina. In young people, pupil diameter can vary from 1.5 to 8 mm, and in older people, pupil excursion is reduced due to fibrosis and atrophy of the muscles that control the pupil.
The use of special drops - mydriatics - allows the pupil to dilate by more than 9 mm.
The structure of the iris
The iris consists of three sheets or layers: anterior border, stromal and posterior pigment-muscular.
When viewed from the front, various features can usually be seen on a person's iris. The highest place is formed by the so-called mesenteries, which divide the iris into two unequal parts, namely: the inner, smaller, pupillary, and the outer, larger, ciliary.
In the pupillary part, enclosed between the mesentery and the pupillary edge, we see a brown border of the epithelium, then the sphincter outward, and even further - the radial branches of the vessels.
The outer ciliary region contains sharply defined lacunae or crypts lying between the vessels, like spokes in a wheel. They are random in nature and appear the clearer the more unevenly distributed the vessels are. In addition to the crypts, grooves can be found on the iris, concentric to the limbus, which are the result of changes in the size of the pupil, especially its dilation.
In the area of the pupillary edge and the “collar” the iris is thicker than at the periphery. With traumatic lesions in the periphery, avulsions often occur - iridodialysis, and the abundance of vessels causes hemorrhages into the chambers of the eye.
The posterior surface of the iris is adjacent to the anterior surface of the lens. In inflammatory diseases, this can lead to the adhesion of pigment cells of the iris to the lens capsule and the formation of so-called posterior synechiae.
Iris color
The color of the iris is determined by the number of melanocytes in the stroma and is an inherited trait. The brown iris is inherited dominantly, and the blue iris is inherited recessively.
Most newborn babies have a light blue iris due to weak pigmentation. By 3-6 months, the number of melanocytes increases and the iris darkens. Albinos have pink irises because they lack melanosomes. Sometimes the irises of both eyes are different in color, which is called heterochromia. Melanocytes in the iris can cause the development of melanomas.
Methods for studying the iris and pupil
Methods for examining the iris and pupil include:
- Inspection with side lighting
- Biomicroscopy – examination under a microscope
- Fluorescein angiography – contrast study of the vasculature
- Pupillometry – determination of pupil diameter
These studies may reveal congenital anomalies:
- Remains of embryonic pupillary membrane
- Coloboma of the iris
- Absence of the iris - aniridia
- Multiple pupils
- Pupil dislocation
- Heterochromia
- Albinism
The list of acquired disorders is also very diverse:
- Posterior synechiae
- Fusion of the pupil
- Circular posterior synechia
- Rubeose
- Trembling of the iris - iridodonesis
- Iris dissection
- Mesodermal dystrophy
- Traumatic changes - iridodialysis
Pupillary changes:
- Mydriasis – pupil dilation
- Miosis - constriction of the pupil
- Anisocoria – uneven pupil width
- Disorders of pupillary movement to light, accommodation and convergence
Raduzhina Dictionary of Russian synonyms. iris noun, number of synonyms: 3 iris (3) ... Synonym dictionary
IRISH, and, female. (specialist.). Same as the iris. Ozhegov's explanatory dictionary. S.I. Ozhegov, N.Yu. Shvedova. 1949 1992 … Ozhegov's Explanatory Dictionary
- (iris, PNA, BNA, JNA; synonym iris) the anterior part of the choroid of the eyeball, located in front of the lens and separating the anterior and posterior chambers of the eye; contains circularly and radially arranged smooth muscle cells... Large medical dictionary
G. Part of the choroid of the eye, located between the cornea and the lens, the color of which distinguishes the color of the eyes; Iris. Ephraim's explanatory dictionary. T. F. Efremova. 2000... Modern explanatory dictionary of the Russian language by Efremova
Iris, irises, irises, irises, iris, irises, iris, irises, iris, iris, irises, iris, irises (Source: “Complete accentuated paradigm according to A. A. Zaliznyak”) ... Forms of words
iris- rainbow, and, genus. p.m. h. zhek... Russian spelling dictionary
AND; pl. genus. zhek, dat. zhkam; and. = Rainbow... encyclopedic Dictionary
IRIS- A pigmented muscular membrane that extends from the ciliary body of the eye. The hole in the center is the pupil, which contracts and dilates to control the amount of light entering the eye... Explanatory dictionary of psychology
Iris- The anterior part of the choroid, a colored disc-shaped membrane lying between the cornea and the lens and consisting of two smooth muscles that regulate the dilation and constriction of the pupil... Psychology of sensations: glossary
iris- And; pl. genus. zhek, dat. zhkam; and. = rainbow... Dictionary of many expressions
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Each of us wonders why people have eyes of different colors. Sometimes, at birth, eyes have one color, but over time they acquire a completely different color. It is also uncommon to find people who have both eyes of different colors, which is associated with insufficient or excess melanin (a coloring substance) in the body. This phenomenon is called heterochromia. So, the iris of the eye is responsible for the change in color and pattern, which we will discuss in more detail later.
Structure and functions of the iris
The eyes, whose structure is quite complex, play an important role in human life. Each of its components performs certain functions, which, in turn, affect visual acuity. In the visual apparatus, everything is interconnected, for example, how the cornea of the eye directly depends on the state of the iris.
The iris is located between the lens and cornea of the eye. The free space between them is filled with chamber liquid. Also, the iris in the center has a hole - the pupil, which is responsible for the amount of light entering the retina, regulated by muscles, namely:
- radial (dilator) - capable of dilating the pupil;
- circular (sphincter) - capable of constricting the pupil.
When studying the structure of the iris of the visual organ, special attention is paid to the term “histology”. What it is? Histology is the detailed study of the layers of the iris.
The histology of the iris involves division into three layers:
- anterior (border);
- medium (stromal or fibrovascular);
- posterior (pigment-muscular).
In this case, the iris performs the following functions:
- Determines image clarity without distortion due to scattered light rays.
- Determines eye color depending on the number of pigment cells.
- Provides constriction or dilation of the pupil depending on the light level.
Attention! The iris tends to change its color and pattern throughout life.
Diagnostic treatment methods
The appearance of spots on the iris or its lightening indicates that a person has degenerative changes in the eye or some health problems. By the color of the iris you can determine the amount of pigment and its condition:
- Blue, cyan, greenish or gray color means low pigment content.
- Brown or black color means high pigment content.
- Yellow color means the presence of liver disease.
- Red or pink color refers to the hue of the incident light from the blood vessels, found among albinos who lack pigment.
If a person has a red iris of the visual organ, this means inflammation of the iris, which occurs as a result of:
- Various types of injuries and burns.
- Previous surgical interventions.
- Allergies.
- Conjunctivitis.
This disease entails pain when pressing on the eyelids, blurred vision, tearing, photophobia (constriction of the pupil), and increased eye pressure.
Important! If you suspect an inflammatory process in the iris, do not self-medicate to avoid harming your eyes, but immediately consult an ophthalmologist who will conduct a full examination and prescribe the correct treatment.
When diagnosing the iris, the following congenital or acquired anomalies can be identified:
- albinism (lack of melanin);
- heterochromia - when the eyes are different colors;
- melanoma is a malignant tumor resulting from the development of pigment cells;
- iridocyclitis;
- polycoria - multiple pupils;
- aniridia - absent iris;
- pupil dislocation (deformation).
In ophthalmology, examination of the condition of the iris is possible:
- External inspection with focal lighting.
- Biomicroscopic - based on the slit rays of a lamp and a microscope, you can examine not only the iris, but also the condition of the lens, conjunctiva, vitreous body, cornea, along with pachymetry, which makes it possible to clearly make an accurate diagnosis.
- Pupillometry - thanks to a telemetric device, the size of the pupil is examined with the dynamics of its changes.
- Gonioscopy is an examination of the anterior chamber of the eye, located between the cornea and iris.
Advice! In case of inflammatory processes of the iris or other eye pathologies, under no circumstances should ultrasound pachymetry of the cornea be performed, which is an instrumental method for measuring the thickness of the cornea.
Having studied the so-called science of histology, namely its structure, as well as functions, diseases that arise as a result of disorders in the iris, we can draw the following conclusion that you need to take your vision seriously, since it is easy to lose, but it will be restored much more difficult.
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