Eye (biophysics)/Principle of vision
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:
- 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:
- yellow spot (macula lutea) – the place of greatest eye sensitivity
- 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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Related articles[edit | edit source]
- Biochemistry of the vision process
- Trichromatic Vision
- Eye (biophysics)
- Eye (biophysics)/Eye defects
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- Retinal detachment
Source[edit | edit source]
- Holešov. Ladislava Jaroše Gymnasium [online]. [cit. 2009-05-23]. <http://www.gymhol.cz/projekt/fyzika/07_soustavy/07_soustavy.htm>.
[edit | edit source]
- 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