Retina

Retina is the innermost layer of the eye and is light sensitive in nature. When we see an object, the light rays pass through the lens in our eyes and fall on the retina. They get converted into neural signals/impulses here and the optic nerve carries these visual stimuli to the brain that translates them back as images. Now if you are a Harry Potter fan, then consider the retina as the platform 9 ¾ (the entry point to the world of magic). If something goes wrong here, then nothing reaches your center for imagination (the brain) and your vision to the beautiful world stays completely cut-off.