After reading the previous posts, i was compelled to further research about the eye, and indeed, i have managed to find out more about the specific and specialised structures and functions of the eye.

Below are some of them,

A more indepth analysis about the retina:
The retina is a 5 square centimeter area in the back of the eye, where all light detection takes place. It consists of over 100 million photo-sensitive rods and cones. The signals created by these rods and cones are then sent via the optic nerve to the brain. The brain then processes these and interprets the message, allowing us to see images.
Rods and Cones react to different levels of light. Cones are photopic, which means that they respond to high light levels. Rods are scotopic, which means they respond to low levels of light. Depending on the amount of light striking the retina, one kind of cell will become more responsive, while the other will "turn off." The human eye has about 7 million cones and 120 million rods. Nocturnal animals, such as cats, have more rods and fewer cones. Many diurnal animals, such as pigeons, only have cones.

Focusing or Accomodation:
Light entering the eye is focused by two lenses: the cornea and the eye lens. The lenses hold their shape due to pressure from the vitreous humor and aqueous humor, as well as a muscle group called the ciliary muscles. Light is refracted by the lenses to focus at the back of the eye. As objects get further away from the eye the ciliary muscles relax, allowing the eye lens to become flatter and bend the light differently. Sometimes, due to age or genetics, the ciliary muscles will not bend the eye lens correctly, causing a blurred image. This condition is called either myopia (nearsightedness) or hyperopia (farsightedness).

Light control:
The iris changes in size to allow different amounts of light to enter your eye.When there is more light, the iris shrinks. This is done by the contraction of the circular muscles and the relaxation of the radial muscles. This blocks out much of the light,and as is demonstrated by the first activity, thisincreases the sharpness of your vision. If there is less light, the circular muscles relax and the radial muscles contract. The iris increases in size, allowing more light to enter the eye to be processed.

If you are still keen to find out more, here's a good website which provides fun activities to test out the different functions of the eye. Go to (http://library.thinkquest.org/27066/theeye/nlstructure.html), and try the experiments out. I hope you all would enjoy them =)

-Benjamin