Ophthalmology

The ophthalmology is the branch of the Médecine in charge of the treatment of the diseases of the eye and its appendices. It is a medico-surgical speciality.

Anatomy and ocular physiology

The eye

As at the Mammalian majority of the S, Bird X, Reptile S and Poisson S, the human eye consists of a Eye-ball, made of 3 envelopes: the sclère, the uvea, and the retina (of outside in inside).

A former segment

  • the Cornea, left former the ocular sphere, is a transparent lens whose role is to collect and to focus the light on the crystalline lens. It is made up, of before behind, of the epithelium, the membrane of Bowman, the stroma, the membrane of Descemet and finally of the endothelium. Its average diameter is of 12 Misters

  • the Uvée, made up of the iris, muscle delimiting the pupil zone " virtuelle" located at the center of the iris, and allowing the modification of the entering luminosity, the Choroid and the Body ciliaire;
  • the Crystalline , lens biological being used for the Accommodation (“developed” on the object to visualize allowing to obtain from a point object a focal point image on the retina) is connected to the bodies ciliaires via the zonule of Zinn; It is this lens which, while being opacified, causes the cataract.
  • the aqueous Humor, liquid located between the posterior face of the cornea and glazed ahead behind. It is secreted by the bodies ciliaires.

A posterior segment

  • the Retina, membrane gathering of the nervous cells photoréceptrices called cones or of the Stick S, being used for the transformation of the electromagnetic Wave into electric impulses, for image processing by the nervous system;

  • the choroid, feeder membrane of the retina and genuine “vascular sponge” which papers the inner face of
  • the Sclère.
  • the Vitreous body, kind of freezing which fills the cavity located behind of the crystalline lens and in front of the retina.

Appendices of the eye

Four:

  1. the orbit, osseous cavity, covered with a membrane fibro-rubber band (the périorbite). Role of protection 

  2. the Muscle S oculomoteurs, role of displacement. 6 at the human :  
    1. 4 right muscles: right superior, right lower, internal rights (or médial) and external right (or side);
    2. 2 oblique muscles: large oblique (or oblique superior) and small oblique (or oblique inferior)
  3. the Eyelid, membrane allowing a more or less important insulation of the electromagnetic Radiation, the spreading out of film of tears and the protection of the cornea.
  4. the lachrymal Gland: located in top and outwards, it secret 40% of our tears, the remainder being secreted by additional glands.

The ophthalmologic examination

A complete ophthalmologic examination includes/understands the interrogation of the patient, and a physical examination.

Vision

The vision is the term which indicates the measurement of the minimum angle of resolution. The normal vision is of 10/10e in each eye.

One uses scales of test to carry out subjective measurements of the vision. For example:

  • scale Monoyer: test in vision by far which uses letters of the alphabet Latin (vision with 3 and 5  m).
  • scale Armaignac and scale Landolt: for the illiterate ones (vision with 5  m), with geometrical figures.
  • scale Pigassou: with drawings, for the children (vision with 2,5  m).
  • scale Parinaud: test in vision of close which uses texts in French language of decreasing size, read to about thirty centimetres of the eyes.
  • Rossano-Weiss scale: test in vision of close which uses images.
  • test of Ishihara: test of the vision of the colors, and not of vision, which uses drawings (figures, reasons) facts with spots of color. This test makes it possible to detect the dyschromatopties (defect of vision of the colors).
The measurement of the vision is carried out in practice with a study of the vision of near and by far, without correction then with.

Field of vision

It can be estimated with the finger, and will be evaluated as well as possible using instrumental methods by Campimétrie or Périmétrie.

Examination of the former segment

It is carried out using a lamp with slit or biomicroscope, it is a painless and noninvasive examination making it possible to study the former segment and the appendices of the eye. It comprises also an examination of the irido-corneal angle.

Measure ocular tonicity

Examination systematically carried out, it makes it possible to detect or follow a glaucome (acute or chronic). The average ocular tension (i.e. the Pressure reigning in the eye) must be ranging between 9 and 21 MmHg, but this value must be balanced by that of the central corneal thickness (pachymetry) and the resistance of the cornea (hysteresy).

Examination of the posterior segment

It is the examination of the bottom of eye, which one carries out after the administration of a Collyre making dilate the pupil (or without dilation). One visualizes in a direct or indirect way thus (according to the material employed) the Rétine and his components: papilla (birthplace of the Optical nerve), mackled (zone of the retina responsible for the vision specifies), Veine S, Artère S, retina peripheral, as well as glazed.

Complementary examinations in ophthalmology

  • Angiographie with the fluorescein and the ocular green of indocyanine

  • Echography
  • Radiography of the orbit (in the case of traumatic pathologies, or certain tumors)
  • Scanner orbital and retro-orbital
  • Electroretinogram
  • visual evoked Potential Electrooculogram
  • OCT. (tomography with optical coherence): technology developped at the point by the MIT in the years 1990 and developed and diffused in the clinical applications especially to the beginning of the year 2000, this examination makes it possible to reconstitute by means of computer microscopic cuts of the retina. Its two principal indications are the study of the attacks of mackled and the tracking and the monitoring of the glaucomes by allowing the measurement of the residual fiberoptic capital at an individual (capital which decrease naturally with the age but which decrease at high speed at the people reached of a glaucome)
  • specular Microscopie: this examination makes it possible to measure the capital of the corneal cells endothéliales (these cells, nonrenewable, paper the posterior face or intern of the cornea which they ensure a normal transparency by regulating the hydration of the cornea)
  • ORA (hysteresy)
  • corneal Topographie: analyzes data-processing corneal surface, it carries out true level lines of surface or posterior face of the cornea: its use is indicated in certain affections of the cornea, the adaptation of contact lenses and the refractive surgery).
  • corneal pachymetry
  • biometrics
  • GDX (laser polarimetry of fiberoptics)

Measuring devices

  • Refracting: simulator of glasses for the subjective measurement of the refraction.
  • Tonometer: measure pressure of the eye.
  • Pachymètre : measure corneal thickness.
  • Frontofocometer: measure power of the corrective lenses.
  • Keratomètre : measure radius of curvature of the cornea.
  • Autoréfractomètre : measurement objectifies refraction.

Ophthalmologic pathologies

Pathologies of the former segment

Pathologies of the retina

Pathologies of the eyelid

Glaucomes

Disorders of the refraction

The disorders of the Réfraction are due to an anomaly of the optical system formed by the Cornée, the Cristallin and the Rétine. In a normal eye, the focal point of the cornea-crystalline lens unit is located on the retina. In vision of close, the capacity of accommodation of the crystalline lens (which bulges), makes it possible to advance the focal point in front of the retina to preserve a concentration on the retina of the luminous rays which are not parallel any more but divergent.

  • Myopia: the focal point is located in front of the retina. The remote objects appear fuzzy.

  • Hypermétropie : the focal point is located behind the retina. The hypermétrope is obliged to adapt permanently to advance the focal point, the close objects appear fuzzy when the capacities of accommodation are exceeded.
  • Astigmatism: the luminous rays are focused in two distinct hearths on the retina. This is generally caused by a irregularity of the cornea which involves a defect of Stigmatisme.
  • Presbyopia: reduction in the capacity of accommodation of the crystalline lens of to ageing. The close objects appear fuzzy because the crystalline lens is not able any more to adapt sufficiently.

They can be corrected by the wearing of corrective lenses or an surgical operation.

Disorders of the Binocular vision and Strabism

The eye troubles binocular and strabism are often closely related to the disorders of the refraction (case of accomodatif strabism for example).

One finds there for example the Hétérophorie, a latent deviation of the visual axes compensated by a reflex of fusion binocular and being able to generate headaches, and even a Diplopie (vision doubles) under certain conditions supporting the decompensation of the phorie.

Also very frequent are imbalances oculomoteurs like the insufficiencies or excess either of convergence or of divergence.

For more information on strabisms, consult the article dedicated " Strabism ".

Eye troubles of the colors

Surgery

History of ophthalmology

History

Ophthalmology, because of the importance of the eye in human perception and the role of the eye in the esthetism of the face, is a very old science. Several techniques developed in many place of the world independently, China, Japan, Central America, Europe, Egypt and India since Antiquity.

One of the oldest documents speaking about ophthalmology and Obstétrique is the Papyrus of Carlsberg. It dates, for its oldest part of.

Famous ophtalmologists

See too

Related articles

External bonds

  • Ophtasurf, the site on ophthalmology an information source on ophthalmology

  • Duplicated National of the College of the University of France and duplicated Ophthalmologists CHU of Pity-Salpêtrière

  • COCNet Ophthalmology Public and professional: to improve the knowledge and knowledge concerning the diseases and the surgery of the eyes

  • historical Sources of ophthalmology

  • Ophthalmology Principal eye diseases and their treatment.

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