The sense of sight
We perceive more than 80% of information from the outside world by our sense of sight. The organ of sight consists of the eye itself and the accessory organs of the eye.
The organ of sight comprises cornea, conjunctiva, sclera, lens, vitreous humour, iris, retina, aqueous humour and many others, such as eye socket, ocular muscles, anterior and posterior chambers, angle of chamber, ciliary body, choroid and optic nerve. The eye socket represents ossteous cavity which contains the eye and it has to protect the eye. Parts of the eye that make its optical system (cornea, aqueous humour, lens, vitreous humour) are important for flawless vision perception.
Light beam transition
Light beams are after transition through all the structures refracted and displayed on retina. If an object is close to an eye, a lens changes curvature, a pupil gets lower and the eyes converge. At the distance vision the pupil gets bigger and the lens gets thicker (and flatter). Light beams are refracted at a point in front of the retina when beeing nearsighted and at a focus behind the retina when beeing farsighted. These vision disorders are corrected by special lens in glasses.
The most common colour vision disorders are congenital and the heredity is sex-linked to men more than to women.
There are approximately 8 % of male population and 0,4 % of female population affected by some kind of colour vision disorder.
Sources:
http://edi.fmph.uniba.sk/~jaskova/IKTH/tema02/tema02.html#farby