Eye is a small window to the big world. Although the eye is small, it is one of the complex organs we have got. There are number of parts working together to make it possible for us to have the binocular vision. Binocular vision is nothing but the unified / fused image from both the eyes.

Light entering the eye is bent or refracted by the cornea passes through the lens and gets focussed on the retina. When the light is sent through a concave lens, the light rays bend away from the centre. Similarly, when the light is sent through a convex lens, the light rays bend towards the centre. The human eye has multiple surfaces that cause the light to bend. If everything goes ok, light makes it through and gets focussed at the retina.

Retina contains two types of cells, rods and cones. Rods are responsible for the night vision (where the light is low) and the cones handle the day vision as well as in a lit environment at night and colour translation. There are about 100 million rods and 7 million cones in the retina. These rods and cones convert the images into electrical signals and send them to the brain's vision centre where they are converted back into images.

Pupil is the opening at the centre of the iris. The amount of light entering the eye and the amount of light coming off the retina depend on the size of the pupil.

Insufficient numbers of colour cones cause the colour blindness. Vitamin A deficiency causes night blindness. When it comes to the visual acuity or a normal vision, the standard is to have 20/20, what it means is that you can read the chart standing at 20 feet distance what a normal person can read at 20 feet.