Crystalline lens

The crystalline is an element of the eye.

Anatomy

The crystalline lens is a biconvex lens, of variable focal distance to carry out the accommodation of the eye (an adaptation of the vision according to the position of the object observed).
A beam of nonelastic ligaments, the Zonule de Zinn, connects it to the muscle ciliaire which, while contracting, deforms it and modifies thus its capacity of Convergence. The index of refraction of the crystalline lens is n=1,44.

Role

The crystalline lens allows the settling and the formation of a clear image of the object on the Rétine.
Not deformed, it allows the vision by far.
Its deformation corresponds to the phenomenon of Accommodation and allows the vision of près.

Pathologies of the crystalline lens

  • the aphakie (in English aphakia): absence of crystalline lens following an surgical operation or a traumatism.

  • retro-cristallinienne fibroplasy (or retro-lentale fibroplasy, disease of Terry; in English retrolentalefibroplasia, Terry' S syndrome), which reaches certain premature, a few months after the birth. The evolution of the retro-cristallinienne fibroplasy is generally done towards blindness (loss of the vision). This affection is supported by a too important oxygen contribution at the premature one.
  • the homocystinurie is an abnormal site of the crystalline lens.
  • the phako-anaphylactic endophtalmy (in English endophthalmitis phaco-allergica) is an ignition of the former room of the eye of aseptic nature due to a wound of the crystalline lens.
  • the syndrome of Frenkel occurring after a traumatism of the eye, with subluxation of the crystalline lens.
  • the disease of Richner-Hanhart or syndrome of Richner-Hanhart, Genetic disease hereditary and recessive, with a palmo-plantar keratosis associated with a delay of growth and a cognitive delay. This disease is due to an absence of an enzyme: Tyrosin amino transférase.
  • iridodonesis or iridodonesis (in English iridodonesis) results in tremors of the irises caused by small movements of the eye.
  • the lentiglobe or lenticone (in English lenticonus) indicates a deformation of the crystalline lens which has surfaces having a curve more shown than at the physiological state.
  • the Syndrome of Marfan with and size formal amendments of the crystalline lens.
  • the microphakie (in English microphakia) indicates a size abnormally small of the crystalline lens.
  • the phacocèle: it is a hernia of the crystalline lens.
  • the sphérophakie (in English spherophakia) indicates a crystalline lens having a spherical aspect.
  • the phacomalacie (in English phacomalacia) indicates the softening of the crystalline lens.
  • the crystalline dystrophy of the cornea of Schnyder is a malformation of the cornea of nature hereditary and family whose transmission is done according to the autosomic mode dominating
  • the syndrome De Weill-Marchesani or syndrome of brachymorphie-sphérophakie is an affection of hereditary, polymalformative nature with a nanism and a brachycephaly.

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