05.B SIGHT
Seeing colour is dependant on the following conditions; the existence of light, the ability of the eye to record and relay colour information. The human eye is special because it has the ability to adapt tomost conditions. It can interpret colour and see in both daylight and night time conditions. The pupil controls howmuch light enters the eye. When light enters our eyes it passes through the lens and hits the retina. This is at the back of the eyeball. It is full of light sensitive cells called rods and cones which are found at the ends of millions of filaments from the optic nerve, and they are either rod-shaped or cone-shaped. We have about 120millions rods in each eye and these are responsible for vision at low light levels. Rods do not discriminate between colours,
but only between light and dark. They are extremely sensitive, and these are themain light receptors that we use in very dim illumination such as moon light. This is why it is hard to identify colours under such conditions. Their response is greatest for blue-green light, and objects that are blue green appear brighter in low light conditions than other colours, such as red and orange which appear darker. The cones aremore responsive to colour. We have about 6million of these in each eye (themajority are huddled together in a small central spot called themacular). Most people have three different types of cones each tuned to different wavelengths; short, middle and long, which are correspondingly sensitive to blue, green and red. Receptors relay information through the optic nerve and into the brain where it is perceived as colour.
Perception differs fromone person to the next and so two people will not see colour in truly the same way. Sometimes there is a fault in the cone cells and this can lead to colour deficiency.
Perception differs fromone person to the next and so two people will not see colour in truly the same way. Sometimes there is a fault in the cone cells and this can lead to colour deficiency.
Retina
Sclera
Choroid
Suspensory ligament
Macula
Cornea
Aqueous humor
Central retinal artery and vein
Pupil
Lens
Iris
Optic nerve
Ciliary body
Hyaloid canal
Vitreous humor
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