Visual sensation begins at the retina, which is the neural tissue located at the back of eyeballs. It has been known that the retina detects light using photoreceptors which are light-sensitive nerve cells.In case of retinal degenerative diseases such as retinitis pigmentosa and age-related macular degeneration, those light sensing neurons are gradually damaged, leading to a profound vision loss. At the moment, no cure is available for the abovementioned ailments. But, microelectronic retinal prostheses can create artificial vision by electrically stimulating remaining retinal neurons, although the prosthetic vision is still far removed from normal vision.