In Optical physiological, one calls accommodation the adaptive ocular modifications making it possible to ensure the clearness of the images for distances different of Vision. At the man and the Mammalian S, accommodation comprises primarily a deformation of the Cristallin in the direction of an increase in the capacity of Réfraction.

The accommodative function

The eye adapts its optical Puissance to its distance from Vision, to have a clear vision, it must increase power when it passes from VL (vision by far) to VP (vision of near). It is accommodation .

Accommodation is carried out thanks to the change of curves of the two faces of the Cristallin. This increase in power is measured in Dioptrie S. The power of the eye increases by 1 dioptre at a distance of 1 meter, 2 dioptres at a distance of 50 cm, etc

The point nearest visible is called Punctum proximum, and the most distant point Punctum remotum.

Muscles

The change of curve of the two faces of the Cristallin is carried out thanks to the action of the Muscles ciliaires: the muscle of Muller and the muscle of Brucke

These muscles are located in the Corps ciliaire S, they act on the Cristallin via the Zonule de Zinn.

  • the muscle of Brucke consists of radiate Fibers

  • the muscle of Muller consists of circular Fibers

They act in an antagonistic way.

Accommodation

VL - > VP

  • the muscle of Muller contracts

  • the muscle of Brucke is slackened while acting on the Zonule de Zinn which slackens: the Cristallin bulges thanks to its elasticity.

Désaccommodation

VP - > VL

  • the muscle of Muller dilates

  • the muscle of Brucke contracts, car on the Zonule de Zinn and causes the flatness of the Cristallin.

Rest

The accommodatif rest is the passive state of the accommodation of the eye, in absence of Stimulation, i.e. when the subject is plunged in the darkness, or when it fixes an empty luminous space. (= rest physiolgic of accommodation).

It is in fact a position of balance between the two muscles of the Corps ciliaire, a position of waiting, corresponding to their natural Tonus. This “accommodatif tonicity” was quantified with a median value of 0.75 Dioptrie S.

Presbyopia

Certain factors contribute to stimulate or inhibit the accommodation of the eye.

  • the color: red-green
  • difficulty of the text: cut + complication
  • the Amétropie of the subject: a short-sighted not corrected adapts less than a emmétrope; a hypermétrope not corrected adapts more than a emmétrope.
  • binocular vision of the subject: weakness of convergence = weakness of accommodation excès=excès

The Presbytie is explained physiologically by 2 causes: the crystalline lens loses its flexibility and can become deformed

Psychology of the development

It is, according to Jean Piaget, one of the two processes of Adaptation. L'" accommodation" , it is when the individual changes to adapt to the medium. The modification can be Mental E and Mineur E. It is preceded by the process of assimilation. The assimilation is initially incomplete, then, after each accommodation, there is a complete assimilation. The assimilation and the accommodation are the two processes which create the Déséquilibre and the balance.

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