As light enters the eye through the transparent cornea, the pupil controls the amount of light which it will let through by contracting or expanding. The light then reaches the
lens
- a flexible transparent body which focuses an upside down
image
on the retina.
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The
retina
translates the energy of the light into neurological impulses and transmits them to the brain. The
retina
is comprised of three layers of nerve cells: ganglions, bipolar cells and light-sensitive photoreceptors.
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Structure of the eye
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The relative position of the three retinal layers.
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photoreceptors
translate the visual stimuli registered within the eye into data which can be processed by the central nervous system. There are two kinds of photoreceptors:
rods
and cones. Rods are responsible for night vision which is monochromatic. |
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Cones are responsible for
color vision
under normal lighting conditions. The part of retina from which the optic nerve stems has no photoreceptors, and is called the fovea or blind spot, since it does not respond to light. |
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A
cross section
of the
retina
at a point between the fovea the far periphery, where there are more
rods
than cones.
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Note the yellow spot over the fovea, the retinal blood vessels and the blind zone where the nerves lead out of the eye ball.
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