The Ophthalmology is the branch of medicine in charge of treating diseases of the eye and its annexes. It is a medical-surgical specialty.
Like most mammals, birds, reptiles and fish, the human eye consists of an eyeball, made of 3 envelopes: sclero-the cornea, the uvea, and the retina (from outside to inside).
An anterior segment
* The cornea, anterior part of the eyeball, is a lens whose role is to capture and focus the light on the retina. It is, from front to rear, the epithelium, the membrane Bowman, the stroma, the Descemet membrane and the endothelium. Its average diameter is 12 mm.
* The uvée composed of the iris, pupil muscle bounding box "virtual" in the center of the iris, allowing the modification of the incoming light, the choroid and the ciliary body;
* The crystalline lens used for biological accommodation ( "development" on the subject to view to obtain an object of a focal image on the retina) is connected to the ciliary body through zonula of the Zinn; This lens, which in s'opacifiant, causing cataracts.
* Aqueous humor, liquid between the posterior surface of the cornea in front and behind the lens. It is secreted by the ciliary body.
A subsequent segment
* Retina, the membrane composed of nerve photoreceptor cells called rods and cones, for the transformation of the light waves into electrical impulses for processing images via the nervous system;
* The choroid, Foodland membrane of the retina and true "vascular sponge" that lines the inside of
* The sclera.
* The vitreous, a kind of gel that fills the cavity located behind the lens and in front of the retina.
The annexes of the eye
At number four:
1. The orbit bone cavity, covered with a fibro-elastic membrane (the periorbite). Protection role
2. Oculomotor muscles, the role of travel. The number 6 in humans:
1. 4 muscles rights: the right upper right lower domestic law (or medial) and right external (or side);
2. 2 oblique muscles: large oblique (oblique or higher) and small oblique (oblique or lower)
3. The lid, allowing isolation membrane more or less electromagnetic radiation, spreading the film of tears and protection of the cornea.
4. Lacrimal gland: at the top and outside, the secret 40% of our tears, the rest being secreted by glands accessories.
The sight test
An ophthalmological examination includes the examination of the patient and a physical examination.
The visual acuity is the term that refers to the extent of the minimum angle of resolution. The normal visual acuity is 10/10e to each eye.
It uses scale test to make subjective measures of visual acuity. For example:
* Monoi scale test in distant vision which uses the Latin alphabet (vision 3 and 5 meters).
* Armaignac scale and scale Landolt: for the illiterate (vision 5 m), with geometric figures.
* Pigassou scale: with drawings, for children (vision to 2.5 m).
* Parinaud scale test in near vision which uses texts in French smaller, read about thirty centimeters eyes.
Rossano-scale * Weiss: test near vision that uses images.
* Ishihara test: test of color vision, not eyesight, which uses drawings (figures, patterns) made with patches of color. This test can detect the dyschromatopties (lack of color vision).
The measure of visual acuity done in practice with a study of vision from near and far, without correction then.
Consideration of the anterior segment
It is made using a slit lamp or slit is a non-invasive and painless to study the anterior segment and the Annexes to the eye. It also includes a review of the irido-corneal angle.
Measuring eye tone
Review systematically, it allows to detect or monitor glaucoma (acute or chronic). Tension average eye (ie pressure prevailing in the eye) must be between 9 and 21 mmHg, but this value must be balanced by that of the central corneal thickness (pachymetry) and resistance corneal (hysteresis).
Consideration of the posterior segment
It is the merits of an eye, can be realized after the administration of an eye that dilate the pupil (or dilated). It shows thus directly or indirectly (as the material used) the retina and its components: papillary (birthplace of the optic nerve), macula (area of the retina responsible for clear vision), veins, arteries, peripheral retina, and the glass.
Additional tests in ophthalmology
* Fluorescein angiography and indocyanine green
* Ultrasound eye
* Radiography of the orbit (in the case of traumatic disorders, or certain tumors)
* Scanner orbital and retro-orbital
* Visual evoked potentials
* OCT (optical coherence tomography) technology developed by MIT in the 1990s and distributed in clinical applications especially in the early 2000s, the review allows a computer to reconstruct microscopic cuts of the retina. Its two main indications are studying the damage of the macula and the screening and monitoring of glaucoma by allowing capital measurement residual optical fiber in an individual (capital which naturally decreases with age but decreases at high speed people with glaucoma)
* Specular Microscopy: This review provides a measure of capital corneal endothelial cells (cells, non-renewable lining the back of neck or internal cornea on which they ensure transparency in regulating normal hydration of the cornea)
* ORA (hysteresis)
* Corneal topography: analysis of the corneal surface, it achieves real curves level of the surface or the posterior surface of the cornea: its use is indicated in certain diseases of the cornea in the adaptation of contact lenses and in refractive surgery).
* Corneal pachymetry
* GDX (laser polarimetry optical fibers)
* Refractor: simulator glasses for the subjective measure of refraction.
* Tonometer: measuring the pressure of the eye.
* Pachymetry: measuring corneal thickness.
* Focimeters: Power measurement glasses.
* Keratometer measure of the radius of curvature of the cornea.
* Autorefractometre: objective measure of refraction.
Anterior segment diseases
* Earlier Uveitis
Diseases of the retina
* Macular degeneration related to age
* Detached retina
* Diabetic retinopathy
* Macular hole
* Occlusion of the central artery of the retina
* Vein occlusion of the central retina
* Best Disease
* Retinoschisis Juvenile X-linked
* Retinitis pigmentosa
* Macular hypoplasia due to a form of albinism
Pathologies of the eyelid
Disorders of refraction
Disorders of refraction is caused by an abnormality optical system formed by the cornea, lens and retina. In a normal eye, the focal point of the entire cornea-lens is located on the retina. In near vision, the power of accommodation of the lens (which bomb), to advance the focal point before the retina to maintain a focus on the retina of light rays are not parallel but different.
* Myopia is the focal point in front of the retina. The distant objects appear blurred.
* Hyperopia: The focal point is located behind the retina. The farsighted is obliged to accommodate ongoing to advance the focal point, close objects appear blurred when the accommodation capacities are exceeded.
* Astigmatism: light rays are focused in two separate homes on the retina. This is usually caused by a defect in the cornea that leads to a lack of stigma.
* Presbyopia: decreased power of the lens of accommodation with aging. Close objects appear blurred because the lens is no longer able to accommodate enough.
They can be corrected by wearing glasses or surgery.
Disorders of binocular vision and strabismus
Disorders of binocular vision and strabismus are often closely related to disorders of refraction (case of strabismus accommodation for example).
There are heterophorie for example, a deviation of latent visual axes offset by a reflex binocular fusion and can cause headaches or even diplopia (double vision) in some conditions for decompensation of phorie.
Also frequent are the oculomotor imbalances such as excess or deficiencies or convergence or divergence.
For more information on strabismus, see dedicated "strabismus".
The products of Ophthalmology
The market for ophthalmic equipment (surgical products, medicines for diseases of the eye, eye drops, solutions for contact lenses) are Moint to $ 19 billion in 2006.
The market for ophthalmic equipment was as follows in 2006:
* Alcon: 24% in 2006 (sold in 2008 by Nestlé Novartis)
* Novartis: 13% (before redemption Alcon in 2008)
* Bausch & Lomb: 12%
* Johnson & Johnson (Vistakon subsidiary): 9%
* Allergan: 8%
* Pfizer: 7%
* AMO: 6%
* Other: 21%
The ophthalmology, because of the importance of the eye in human perception and the role of the eye in the facial aesthetics, is a very old science. Several techniques have been developed in many parts of the world independently, China, Japan, Central America, Europe, Egypt and India since antiquity.
One of the oldest documents speaking of ophthalmology and obstetrics is the papyrus Carlsberg. It dates to its most ancient of the second millennium BC. AD.(W3C)
Read also Eye