, and they're really essential for photoreceptor health and photoreceptor survival.and several blinding eye diseases involve and their treatments involve these pigment epithelial cells in the retina. we're going to hear about these cells. i think they're going to feature really quite large in our conversation. >> charlie: that's enormously helpful. thank you very much, a huge understanding of how we see and how important the brain is and how important the pathways are. i want to come now to jean and talk about -- we mentioned gene therapy, stem cell therapy and other things. how can gene therapy be helpful? >> well, carla set the stage for this perfectly because she explained how the pigment epithelium provides a nerve function for the photoreceptors, provides nutrients to the cells, taking away waste products, and the two cell types are interdependent so that if there's a problem in function of one particular gene and one of those cells it affects the other cells secondarily. so in the next image is an illustration of one particular example where a mutation can caus

those are called the photoreceptors, and there are two kinds of photoreceptors. there are the rods and there are the cones. the cones are the photoreceptors. the rods are in the macula. the rods are the photoreceptors in the peripheral retina and they are essential for high sensitivity vision. the next step of visual information processing is that the information from the photoreceptors is passed along to the bipolar cells. from the bipolar cells, the information is passed along to the ganglion cells. they are the nerve cells that send their long fibers out into the optic nerve and into the optic track, into the central visual pathways. the last important point i want to make is there is another critical cell type in the retina, called the pigment epithelium. those cells essentially provide crucial support and nutrients to the photoreceptors. they are really essential for photoreceptor health and survival. several blinding eye diseases involve -- and their treatments involve these pigment epithelial cells in the retina. i think they will feature quite large in ou