Light must pass a series of structures for the brain being able to interpret the data that comes from the eyes. The order that light stimuli travels from the eye to the brain is as follows:
1. cornea
2. retina
3. rods and cones
4. ganglion cells
5. optic nerve
6. thalamus
7. primary visual cortex
Light enters trough the cornea, the transparent front part of the eye that covers two-thirds of its total optical power; then it goes to the retina which receives the image that could go to the rods or the cones (depending if the light is at low or high levels, respectively). Then, ganglion cells increase the rate of the impulse within the optic nerve, and finally thalamus passes the sensory signal to the primary visual cortex. In this area of the brain, the basic visual features are extracted and interpreted.
