Simple anatomy of the eye

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Schematic of the eye cut in half:
1. Conjunctiva, 2. Sclera, 3. Cornea, 4 Aqueous humor, 5. Lens, 6. Pupil, 7. Uvea (with 8. Iris 9. Ciliary body, 10. Choroid), 11. Vitreous, 12. Retina (with 13. Macula), 14. Optic disc, 15 Optic nerve

Parts of the eye

Anterior segment

The anterior segment is the third front of the eye including the cornea, iris, ciliary body and lens.

Posterior segment

The posterior segment corresponds to the posterior two thirds of the eye, including the vitreous, retina, choroid and optic nerve.

Eye components

Tear

The tear is a layer of liquid on the surface of the eye, coating the conjunctiva and cornea. Its function is to nourish and protect the eye and enable viewing. The tear brings nutrients and oxygen to the conjunctiva and cornea for healthy manternerlas. The tear makes a protective activity of the eye to the outside elements can drag debris and foreign objects are in the conjunctiva to facilitate its removal. When the eye is irritated lacrimation increased to facilitate the resolution of the picture. It has enzymes and antibodies to slow the growth of microorganisms and bacteria in the eye.

The tear has a function and refractive optical contact with the cornea, to get a smooth surface without friction, affects visual acuity very important way. A bad tear, an irritated eye or dry eye can cause vision problems.

The tear quality depends on the correct composition of liquids, mucus and fat elements produced in glands and eyelids conjunctiva. In some situations the tear quality may be insufficient and further discomfort and irritation may occur.

Diseases
The tear may be found in greater amounts when the eye is irritated and sometimes tear when the eye causes poor quality. There may also be fewer tears when dry eye, which can cause discomfort, infections and eye injuries and reduce the quality of vision is presented.

Conjunctiva

The conjunctiva is a transparent layer covering the surface of the eye from the start of the cornea to the inner eyelids. Its function is to protect the eye and put lubricating oil. The conjunctiva is a mucous layer that produce tears and mucus that moisturize the eye and makes eye protection from external elements. The color of the conjunctiva is transparent and normally gives a white appearance to the eye but may become red from the large number of vessels that have to perform their duties.

Diseases
The conjunctiva can become irritated infections, allergies, inflammation or trauma causing conjunctivitis.

Sclera

The sclera is a thick layer of white, which is the outermost layer of the eye. Its function is to protect the eye and shape and consistency to be the most resistant layer. The conjunctive covers the sclera. The sclera under normal conditions gives a white appearance to the eye.

Diseases
The sclera can become irritated infections, allergies, inflammation or trauma causing inflammation conjunctivitis more localized to the sclera.

Cornea

The cornea is the transparent front part of the eye that covers the anterior segment. It has an optical and protective function. The cornea has a refractive ability which makes it an important part together with the lens to allow the passage of light and correctly projecting light rays on the retina.

The cornea is composed of different layers, well-organized to keep its properties. The epithelium is a surface layer of the cornea to be continuously regenerated, and is in contact with the tear, have a large number of nerve fibers which explains the great sensitivity of the eye. The stroma is an intermediate layer which provides the consistency of the cornea and gives the property of transparency. The inner layers include endothelium does not regenerate and is very important for the proper functioning and nutrition of the cornea. The number of endothelial cells gradually diminishes with age and can be affected by other conditions of the cornea.

Diseases
The cornea is normally transparent to permit the passage of light without impediments. Some conditions of the cornea, trauma and inflammation may affect transparency and decreased vision. Corneal transplantation can change diseased tissues are healthy ones.
The corneal surgery focuses on stromal layer. Laser surgery reshapes the way to allow for refractive eye. Corneal rings are placed in the stroma to stabilize the cornea.

Aqueous humor

The aqueous humor is the fluid found in the anterior chamber is located between the cornea, the iris and the lens. The content of the aqueous humor is mainly water with some proteins, enzymes and electrolytes. Its function is to nourish and oxygenate the cornea and lens, they have no circulation.

The aqueous humor exerts a force against the wall of the eye and ocular maintains the structure and tone. The balance between production and reabsorption of ocular fluid determines the level of eye pressure.

Diseases
The high intraocular pressure which the eye does not mean you have glaucoma but it is the main risk factor for the progression of damage to the optic nerve. It is important to control for changes that would indicate the onset of a glaucoma. Half of patients with glaucoma have high eye pressure when examined first. Early diagnosis and treatment of glaucoma can deliver better results.
Glaucoma surgery facilitates drainage of aqueous humor lowering eye pressure.

Lens

The lens is a natural lens which is located in the anterior segment, behind the iris and in front of the retina. The lens is located within a membrane, called the capsular bag; while it is subject to a fine and elastic fibers, called zonular fibers, which anchor the lens in the uvea. Optical function has the focus and vision. The lens has a refractive ability makes him a very important part in conjunction with the cornea to allow for the passage of light and correctly projecting light rays on the retina. The lens also allows the approach of objects at different distances to obtain a good image through accommodation. The accommodation allows you to change the refractive power of the eye through movements and changes in the curvature of the lens. For near objects, the eye needs additional power, which is obtained by increasing the thickness and decreasing diameter and tension of the zonular fibers. The accommodation capacity is lost gradually and presbyopia or eyestrain from age 40 appears.

Diseases
The lens is normally transparent but over the years will opacified and cataract appears. The pupil dilates in some visual examinations to allow review of the previous segment and assessing cataract. If the cataract is very large it may be that the retina can not be evaluated until after the operation. In cataract surgery the lens is replaced with an intraocular lens to comply with lens functions. Intraocular lenses can be special to decrease the patient's refractive error.

Pupil

The pupil is the central aperture of the iris which allows passage of the light into the eye. Its function is to regulate the amount of light entering like a diaphragm of a camera, in bright light the pupil contracts and dilates in the dark by the action of different muscles and nerve fibers. The pupil dilates in some visual examinations to allow review of the anterior segment, the assessment of cataract and retina.

The pupil is normally black but sometimes color can be seen especially in the presence of a waterfall that you can see through and obstructs the passage of light. The pupil may appear red in flash photography and low light by the reflection of the retina that is red and pupil dilation.

Diseases
The pupil diameter is normally from 3 to 4 millimeters. The pupil size can be changed in some conditions such as inflammation, trauma or tumors.

Uvea

The uvea is an inner layer of the eye which is formed by the iris, ciliary body, and choroid.

Iris

The iris is the colored circle inside the eye having a central opening called pupil membrane. The iris is the anterior part of the uvea and separates the anterior segment of the eye, the cornea of the lens. Its function is to regulate the amount of light entering like a diaphragm of a camera, in bright light the pupil contracts and dilates in the dark by the action of different muscles and nerve fibers. The iris has different colors depending on the pigment (melanin). The pupil dilates in some visual examinations to allow review of the anterior segment, the assessment of cataract and retina.

Iris diseases
The iris color and size can be changed in some conditions such as inflammation, trauma or tumors.

Ciliary body

The ciliary body is the anterior part of the uvea which lies between the iris and the anterior edge of the retina. Its function is to produce aqueous humor in the eye.

Choroid

The choroid is the posterior part of the uvea and is in contact with the retina. Its function is to provide nutrients and oxygen to the retina.

Uvea diseases
The uvea contains many blood vessels so it is very sensitive to inflammation called uveitis. The inflammation of the uvea can affect eye tissues with which it is in contact and can be put into engagement major vision by damaging the retina, the lens and the cornea. The inflammation in the eye can occur in the conjunctiva causing red eye and corneal opacity and can cause injury. In the anterior segment inflammatory cells can be seen, changes of pressure in the eye and shape changes in the iris. A cataract can occur before and have different characteristics. May affect the retina and retinal detachment present, accumulations of inflammation, macular edema or opacities and others. Also the optic nerve can be damaged.

Vitreous

The vitreous gel is located on the back of the eye between the retina and the lens. The content of the glass is essentially water with some proteins, enzymes and electrolytes. The vitreous is not renewed, no production or elimination throughout life, remaining at birth. Its function is to allow viewing and maintain eye tone.

Diseases
The vitreous is normally transparent to allow viewing without hindrances, although it can affect different conditions. Fly spots (vitreous detachment) are collections of glass found inside the eye and are floating. The spots you see are actually the shadows of the gel accumulations projected on the retina. The accumulation of gel are produced along with changes in gel structure. A blood-filled eye hemorrhage and vitreous blocks vision, the most common cause is diabetic retinopathy.
The vitreous is also important in retinal detachment. Through retinal tears an inlet of vitreous located inside the eye occurs, passing underneath the retina and cause the lifting and retinal detachment.
Vitrectomy is the surgical procedure that removes the vitreous and allows manipulation of the retina to resolve the sufferings of the retina.

Retina

The retina is the light sensitive tissue at the back of the eye, coating the interior. Its function is to detect visual stimuli and transmit them through the optic nerve to the brain as nerve impulses. The retina consists of different layers formed by millions of neurons and cells. Photoreceptor cells (rods and cones) are responsible for capturing images and trigger a series of chemical and electrical phenomena. Cones process information from the pigment colors red, green and blue sticks correspond to the amount of light. The retinal pigment epithelium is responsible for providing the functions of rods and cones. The structure of the retina at the cellular level can be viewed through optical coherence tomography. The pupil dilates in some visual examinations to allow review of the anterior segment, the assessment of cataract and retina. The retina has a rich flow that comes in part from the choroid and gives an orange red background staining. The vessels of the retina within the eye arise near the optic nerve are arteries and veins, which are distributed in parallel becoming progressively narrower.

Diseases
The function of the retina may be affected by problems in the retinal cells as retinitis pigmentosa or which may appear over the years such as macular degeneration.
The vessels of the retina can be affected by vascular diseases such as arterial or venous occlusions.

Macula

The macula is the central area of ​​the retina, in the space located between the main vessels. It has the function of central vision that allows you to see fine details and make precise activities such as reading, driving, or view details of a face. A large number of specialized cells (cones) in a characteristic distribution found.

Macular diseases
The macula may have conditions such as macular degeneration, retinal membrane or macular hole affecting central vision.

Optic nerve

The optic nerve is the nerve that connects the eye to the brain. Its function is to transmit information from the retina to specific areas of the brain to allow vision. The optic nerve is formed of different nerve fibers belonging to the brain, therefore optic nerve injuries not regenerate.

Optic disc

The optic disc is the optic nerve at eye level. On examination is seen as a pink disk in the back of the eye of 2.5 mm diameter. The optic nerve is a central excavation is of a lighter color and around the origin of the vessels of the retina is located.

The examination of the optic nerve at eye level can be realized from the form and function. The shape of the optic nerve is titrated with a standard eye examination or retinal tomography studies and in some cases it may be necessary to perform imaging studies to assess the course of the optic nerve that passes into the brain. The optic nerve function is assessed with visual acuity, visual fields, color vision, and eye reflexes.

Diseases
The optic nerve can be affected by diseases of the eye and brain. The most important of the eye condition affecting the optic nerve is glaucoma, which causes changes in form and function. The shape of the optic nerve in glaucoma typically seen with increased central excavations. Vision can be progressively deteriorating and typically affects the periphery to the center, and can lead to blindness. Many cases of glaucoma do not give statements until they are very advanced, it is known as a silent disease.