Retina. Light micrograph (LM) of a section through a retina. The eye works by allowing light to be focused by the lens onto the retina. The retina contains specialised light sensitive photoreceptor cells (top) used to distinguish between colours (cone cells) and to see at night (rod cells). The light is relayed as electrical signals through sensory nerve cells, called bipolar cells ( centre purple cells). The two layers above and below the bipolar nerve cells are synaptic layers, where the dendrites and axons of the photoreceptors and neurons pass on the signals to others below them. The lowest layers are made up of ganglion nerve cells which pass the signals to the brain and the choroid layer that lines the inside of the eye underneath the retina and is pigmented to prevent light reflecting inside the eye distorting the image. Magnification: x120 when printed 10cm wide.