<P> Light entering the eye is refracted as it passes through the cornea . It then passes through the pupil (controlled by the iris) and is further refracted by the lens . The cornea and lens act together as a compound lens to project an inverted image onto the retina . </P> <P> The retina consists of a large number of photoreceptor cells which contain particular protein molecules called opsins . In humans, two types of opsins are involved in conscious vision: rod opsins and cone opsins . (A third type, melanopsin in some of the retinal ganglion cells (RGC), part of the body clock mechanism, is probably not involved in conscious vision, as these RGC do not project to the lateral geniculate nucleus but to the pretectal olivary nucleus .) An opsin absorbs a photon (a particle of light) and transmits a signal to the cell through a signal transduction pathway, resulting in hyper - polarization of the photoreceptor . </P> <P> Rods and cones differ in function . Rods are found primarily in the periphery of the retina and are used to see at low levels of light . Cones are found primarily in the center (or fovea) of the retina . There are three types of cones that differ in the wavelengths of light they absorb; they are usually called short or blue, middle or green, and long or red . Cones are used primarily to distinguish color and other features of the visual world at normal levels of light . </P> <P> In the retina, the photo - receptors synapse directly onto bipolar cells, which in turn synapse onto ganglion cells of the outermost layer, which will then conduct action potentials to the brain . A significant amount of visual processing arises from the patterns of communication between neurons in the retina . About 130 million photo - receptors absorb light, yet roughly 1.2 million axons of ganglion cells transmit information from the retina to the brain . The processing in the retina includes the formation of center - surround receptive fields of bipolar and ganglion cells in the retina, as well as convergence and divergence from photoreceptor to bipolar cell . In addition, other neurons in the retina, particularly horizontal and amacrine cells, transmit information laterally (from a neuron in one layer to an adjacent neuron in the same layer), resulting in more complex receptive fields that can be either indifferent to color and sensitive to motion or sensitive to color and indifferent to motion . </P>

Where does the second pathway of visual information go before it goes to the cortex