The concept of limb eyes is not familiar to the average layman. This is a medical term, and it is rarely seen when visiting an ophthalmologist. Limb - a place where the cornea of the eye passes into the sclera, is involved in the nutrition of the cornea. Despite its small size, it plays an important role in the functioning of the eyeball.
Eye structure
The eyeball is located in the orbit and has a spherical shape. Weight in an adult ranges from 7 to 8 grams. At first glance, the eye consists of two integumentary and three main membranes. But in fact, its structure is very complex. Studying the interaction of tissues and parts of the eye allows us to understand its work.
The fibrous membrane consists of the cornea and sclera, which differ from each other in structure and functions. The connecting link between them is the limb of the eye. Anatomy shows that this zone looks like a ring up to 1 mm wide.
Part of the choroid are the iris, ciliary body and choroid. The iris has a disk shape with a pupil in the center. Its thickness is 0.2-0.4 mm. The most sensitive place of the cornea is the connection with the ciliary body. In severe injuries, a rupture occurs in this place.
The ciliary body is located behind the iris, it is not visible during visual inspection. And with the help of many hairs, the lens is supported. The vascular part of the ciliary body consists of long ciliary arteries. The oculomotor nerve is responsible for the movement and sensitivity of it and the iris.
The choroid is a choroid formed by the posterior short ciliary arteries. It has no nerve endings, its location contributes to the subsidence of pathogens. The choroid easily exfoliates from the sclera.
The inner shell is called the retina and is responsible for the receptivity of information via photoreceptors. The lens is a translucent lens enclosed in a capsule and important for full vision.
Cornea
To understand the limb of the eye, what it is, you should study the structure of the cornea. Its front part is transparent. The limb is located at the point of attachment to the sclera. Its presence is explained by the fact that the deep layers of the cornea are slightly farther than the front. The limb contains many vessels for the nutrition and growth of the epithelium. With a violation of the production of its stem or germ cells, visual impairment occurs.
The cornea has a spherical shape, is devoid of blood vessels, has high pain sensitivity, but does not feel temperature changes. With closed eyelids, the temperature of the limb is 35 ° C, with open 30 ° C, which is an excellent environment for the development of molds that provoke keratitis.
The cornea is fed through the vascular network of the ciliary arteries and lacrimal fluid.
Sclera
Sclera is the opaque part of the shell of the eyeball. The inner layers form the lattice plate, through which axons pass, forming the trunk of the nerve.
The sclera is quite vulnerable to mechanical stress and intraocular pressure. Its thickness in the region of the cornea is 0.6 mm. In the area of the limb of the eye, the cornea, sclera and conjunctiva of the eyeball merge. Therefore, this zone is the starting point for the development of pathologies and inflammations of the eyeball. Allergic reactions, papillomas, melanomas, or developmental abnormalities may appear. The limb zone contains the anterior ciliary arteries, due to which an edge vascular network is formed. Along its circumference are the nerve plexuses of long and short ciliary nerves. The sclera does not contain nerve endings, pathological processes often occur in it.
Conjunctiva
The conjunctiva is the mucous membrane that covers the posterior surface of the eyelids. In this case, it passes to the front surface of the eyeball and ends in the limb of the eye. Its main purpose is to connect the eyelid and eye.
The conjunctival leaf becomes larger with closed eyes, with open it decreases markedly. The transitional fold is covered with several layers of squamous epithelium with a large number of mucous cells. The conjunctival tissue is loose and contains lymphocytes. Due to the connection with the sclera, the tissue easily moves along the surface.
The part of the conjunctiva belonging to the limb of the eye contains epithelial islets with Becher cells. Radially to the study area are cells producing mucin. Blood supply occurs due to vascular trunks extending from the arteries. The main trunks of the ciliary arteries do not intersect with the limb.
The conjunctiva contains a large number of lymphatic vessels. From them, the lymph drains into the anterior and submandibular nodes. Due to the large number of nerves, this part has an increased sensitivity.
Eyeball muscles
The muscle apparatus of the eye consists of three pairs of muscles:
- straight upper and lower;
- direct internal and external;
- oblique upper and lower.
All but the lower oblique are woven with tendons into the sclera. The distance from the muscle to the limb of the cornea of the eye has its own, ranging from 5.5 mm to 8 mm. The superior oblique muscle passes through the angle of the orbit and attaches to the sclera of the eyeball at a distance of 16 mm from the limbus.
The lower oblique muscle starts from the lower bone wall of the orbit, attaches to the sclera at a distance of 16 mm from the limbus. With muscle contraction, the movement of the eyeball occurs. Eye movements occur up, down, left, right. At the same time, the apple is fixed, the conditions for the work of the cortical analyzer are created, the mesh image turns into a single image.
Eyeball limb
Now is the time to familiarize yourself with the features of the junction of the cornea, conjunctiva and sclera. Actually, this is the main function of the limb of the eye. Because of this, it is the site of infections and pathological processes, including cancerous tumors.
The limb epithelium thickens due to an increase in the number of layers. Cells in this case have a small shape and are located very close to each other. The lower border of the epithelium is wavy. Connective tissue contains nerve endings.
On one side is a layer of blood vessels and surface branches. The limb region contains many branches of nerve endings. Then they penetrate the cornea.
If negative processes occur in the area of the limb of the eye, the photo of the ophthalmologist shows that the negative effect extends to his vessels and nerve plexuses, which leads to severe lesions of the cornea. The sclera takes on the protective function of the organ of vision, its density and thickness are not the same throughout the area.
Spring qatar
It is known that the limb of the eye is the place in which the cornea, sclera and conjunctiva communicate. Articulation and fever allow the development of various infections and pathologies.
One of the varieties of trouble is spring Qatar. The disease occurs at the age of 5 years in the spring or summer. It occurs most often in boys. It is believed that ultraviolet rays become the cause of the disease. Symptoms disappear as they grow older.
With this disease, the growth of limb tissue occurs. It turns into a yellow-gray surface. Visually, the color changes, a small roller appears above the limb. In addition, the growth of the conjunctiva may occur. To reduce symptoms, you should avoid the effects of ultraviolet rays and use sunglasses.
A similar reaction can occur due to an allergy to medications. In this case, antihistamines and vasoconstrictor drugs are used.
Conjunctivitis
Deviations of the limb of the eye occur with chlamydial conjunctivitis. The causative agent is Chlamydia trachomatis. You can get infected through the household, through dirty hands. Infection with eye contact is almost always striking. The incubation period lasts no more than 2 weeks. The chronic course alternates with periods of exacerbation and remission.
The color of the conjunctiva becomes burgundy, follicles develop in the area of the study area and the inflammation passes to the cornea. At the same time, a dark rim appeared around the limb of the eye. Individual follicles began to die. The appearance of keratitis with the ingrowth of blood vessels in the cornea is characteristic. The process fades with scarring of the tissue. In the future, the development of complications is possible, in the absence of treatment up to complete loss of vision.
Benign tumors and papillomas
A corneal or conjunctival tumor is directly related to the limbus. Most often located directly on it or in close proximity. The tumor spreads through the cornea and can reach the deep layers, affects the blood vessels. Its surface can be smooth, white, with deviations in the limb of the eye. It becomes uneven and bright. When examining a tumor, particles of sweat, adipose tissue and hair are found in it.
Papillomas are manifested by small nodules on the conjunctiva. Nodules are mobile and easily damaged. The development of papilloma in older patients occurs near or on the limbus. At the same time, a white dot appears on the studied area, which changes its shape. The surface of the papilloma is rough, then spreads to the cornea.
Inside the neoplasm, vascular loops can be detected. Neoplasms may themselves disappear. Surgical treatment is ineffective, using a laser to avoid papilloma overgrowing into a cancerous tumor. After removal of the neoplasm, vision does not disappear, relapses rarely occur.
Xerophthalmia
Xerophthalmia is a disease in which the conjunctiva and cornea of the eyes dry out. Softening leads to the breakdown of the mucosa. The reason for this is an excessive load on the eyes, working at a computer, and a long stay in smoky rooms. The cause of the development of the disease is a deficiency of vitamin A.
Depending on the degree of damage, the dryness of the membrane changes. With deep xerosis, roughness is manifested. The cornea becomes cloudy, the eye limb is uneven. Around it appear white plaques resembling foam.
If at this moment a bacterial infection joins, then the risk of corneal ulcer is high. There is a burning sensation and visual impairment.
To get rid of xerophthalmia, drugs with a high content of vitamin A are prescribed. Recovery depends on the severity of the lesion. If the disease affects only the upper layers, then it occurs quickly. With the appearance of limb irregularities, clouding of the cornea, a decrease in vision may occur.
Wide limb
At the moment, this pathology is considered an abnormality that is congenital or acquired in the future. Wide limb eyes, what is it? The norm is 1 mm, but there are situations in which the indicator can be much larger.
A similar pathology occurs in patients with epilepsy and disorders of the nervous system. The wide limb is different in color. Normally, a shallow circular groove serves as the boundary between the cornea and the eye protein. It is often noted that the limb of the eye is dark and visible to the naked eye.
Examination of patients with a wide limb revealed no deviations in the development of the organs of vision. It is still unclear why the changes in the limbus occur and how this affects the eyeball.
Diseases in which deformation occurs
With an increase in the vessels of the eyeball, a conjunctival infection develops. In this case, the conjunctiva has a red color, which turns pink in the limb area. Its size and shape do not change.
Pericorneal infection is characterized by vasodilation along the edge of the cornea. There is a frame around the limb, it seems that it is painted in pink and purple. Toward the edges of the eye, the color intensity decreases.
With a number of diseases, deformation of the eyeball occurs. If progress has been stopped, residual deformation may occur. The eyeball is compressed, the shape changes from a ball to an ellipse.
Limbal hyperemia occurs when wearing soft contact lenses, characterized by vasodilation in the limb of the eye. In this case, dark shells appear there. The reason for this is the lack of oxygen in the tissues of the eyeball.
Those who wear contact lenses are at increased risk of developing sterile corneal infiltrates. As a result, the vessels of the limb expand, the inflamed cells continue to move around the eye.
Congenital glaucoma is a disease diagnosed in the first year of a child's life. Increased intraocular pressure leads to stretching of the cornea, swelling. For this reason, the child is afraid of light, lacrimation and redness of the eye occurs. A characteristic sign of the progression of the disease is atrophy of the stroma of the iris, limb distension, clouding of the cornea, the appearance of blood vessels. The risk of corneal ulcers increases.