Retina

The rear section of the eye onto which light is focused. It contains photoreceptors: cones, rods and ganglion cells which express melanopsin. The cones and rods are cells or neurones which are sensitive to visible light. The cones (there are around 6 million on a human retina), which transform the electromagnetic signal of light into an electrical signal, assure diurnal vision and the vision of colours. The rods (around 125 million) assure nocturnal vision and vision in conditions of low light intensity but do not perceive colours. Thanks to these two types of cell, the brain can interpret the signal and construct vision.