T.I.E.T.

The retina is a disc shaped collection of neurones, some of which are photo-sensitive, at the back of the eye. Covering about 72% of the eyeball, it is composed of layers of neurones and synapses, like a layered cake.

The optics of the eye create an image of the visual world on the retina, which serves much the same function as the film in a camera. (In fact the image which falls on the retina is upside down, and your brain is smart enough to flip the image the right way up.)

Light striking the retina initiates a cascade of chemical and electrical events that ultimately trigger nerve impulses. These are sent to various visual centers of the brain through the fibers of the optic nerve.The retina is the only part of the brain which is outside the skull. It grows out of the optic nerve which connects to the visual cortex of the brain.

The Photoreceptor Layer is composed of Rods (for night vision) and Cones (for finely detailed imaging in the light). The light is absorbed by the rods and cones and begins a process of information signaling that sends signals through a web of nerve cells that are in contact with the rods and cones. The information is directed indirectly, to the Retinal Ganglion Cells (RGC), which ultimately form the Optic Nerve.

Neurons that are directly sensitive to light are called photoreceptor cells. There are two main types: rods and cones. Rods function mainly in dim light and provide black-and-white vision, while cones support daytime vision and the perception of colour. A third, much rarer type of photoreceptor, the photosensitive ganglion cell, is important for reflexive responses to bright daylight.