Eye (biophysics)/Principle of vision

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The eye is a combined optical system with a variable focal length. The resulting image is reduced, inverted and real.

  • when the beam enters the eye, the light passes through the cornea and ocular fluid
  • variable opening in the iris controls the intensity of incident light
  • after passing through the lens (the largest refractive index of all parts of the eye) the light spreads with the vitreous (smallest refractive index)
  • the image formed on the retina, in which there are two types of cells:
  1. rods (perceive light intensity)
  2. cones (perceive colors)
Here are the endings of the of the optic nerve, that carry sensations to the brain.
  • two main points are used to orient the eye doctor on the retina:
  1. yellow spot (macula lutea) – the place of greatest eye sensitivity
  2. blind spot (discus nervi optici; papilla nervi optici) – place where the optic nerve enters the eye, i.e. a place where there are no sticks or suppositories
  • the emergence of a sharp image is made possible by accommodating ability of the lens, which is held by the ciliary muscle, which changes the curvature of the optical surfaces as needed (at a long distance, less curvature and vice versa):
  • when looking at a far point (infinity) the accommodation of the eye is minimal
  • when looking at the near point (up to 15 cm), the accommodation of the eye is maximum
  • Conventional visual distance = 25 cm.

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  • Kymplová Jaroslava: Biophysics visions. Multimedia support for the teaching of clinical and medical fields :: Portal of the 1st Faculty of Medicine of Charles University in Prague [online] 2/19/2008, last update 2/19/2008 [cit. 2011-12-22] Available from WWW: <https://portal.lf1.cuni.cz/clanek-809-biofyzika-videni>. ISSN 1803-6619