Explain the structure and working of …

Sclera-this is the outer Court of the eye covering the eyeball which is white and tough. It protects the interior of the eye from injuries due to accidents Cornea-the transparent front part of sclera is called cornea. It is clear like glas and has no blood vessels in it. Iris and pupil-behind the cornea, there is a dark muscular structure called Iris in it . The size of The Pupil is controlled by the Iris. The Iris is the part of eye which gives it its distinctive colour. When we say that a person has a green eye, it refers actually to the colour of the Iris. The Iris control the amount of light entering in our eyes. Lens and retina-Behind The Pupil of the eye, there is a lens which is thicker at the centre that is a convex lens. The lens focuses light at the back of the eye on a layer called retina. Retina is like a movie screen which shows the picture we see. Retina contains several Nerve cells. Sensations felt by the nerve cell are then transmittedto the Brain through the optic nerve. Optic nerve is like the cable that carries all the pictures to the brain. There are two kinds of cell in the retina- Cones - these are sensitive to bright light and sense colour. Rods- these are sensitive to dim light and sense black and white. Blindspot-at the junction of the optic nerve and the retina there are no sensory cells so no vision is possible at that spot .this is called the blind spot.