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how the eye works
The eye allows us to see, judge distances and provides one of the essential sences.
It gives us a great awareness of our environment and is
thought to be a great peice of natural engineering.
The eye consists of a few main parts, the iris, pupil, lense,vitriouse humour and retina. I
will explain how each one works.
Iris: This can appear different colours on the outer eye. It expands and contracts in
relation to the muscles which control the movement of the lense.
pupil: Most of the light travels into the eye through this. Its colour is black.
lense: this is one of the most the most important parts of the eye, its function is to focus
light onto the centre of the retina. It is moved by two ligaments (muscles) located on the
edges. Irregularities in this can cause long or short-sightedness.
vitriouse humour (sometimes just vitrious): this is the white, jelly like substance found
surrounding the parts of the eye.
retina: the part of the eye that picks up light patterns and sends them to the eye, it is
important that an image is focused exactly onto this to see properley. The retina is made
up of cones and rods, the rods detect dim lights in black and white and the cones detect
bright lights and colour using colour sensitive pigments which use colour wave
length(measured in nanometers). each rod detects a different colour, If there are more
rods for one couler than another couler blindness can result.
We need to have two eyes so that the brain can work out distances by the amount they
point inwards to each other.
how we achieve vision
we see when light bouncing of an object travels into the eye via the pupil, when it enters
the eye it is first focused by the lens onto the retina, where rodsa and cones detect the
pattern of the light and send it via the optical nerve to the brain where it is decoded into
what we see. When an image reaches the brain it is upside down, our brain turns it over
automatically.
shortsightedness (myopia)
near-sightedness, like farsightedness is caused by an image not being focused exactly on
the lense, in shortsightedness, the image is focused to close to the lense, meaning it is too
far from the retina, this can be corrected by a convex lense.
Longsightedness (hyperopia)
This is very much like Shortsightedness, except the image is focused too far away from
the lense, making it actually behind the retina. This can be caused by the eye being too
long, as is my experience, or the lense being irregular. This can be corrected by a concave
lense.
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