Nervous system has strong plasticity, when the main visual processing area V1 damaged, projection through the corpus callosum and pulvinar to the parietal lobe and temporal lobe areas which are alternative visual pathways, will help patients recover part of the visual function. The specific areas of the ventral pathway of the visual center can be identified for the face, object or visual scene, and the dorsal pathway is selective for visual spatial positioning. Bilateral occipital lobe injury may present complete visual loss (cortical blindness), but patients are unable to recognize their defects. A person whose ventral pathway was impaired but had intact dorsal pathway perceived visual agnosia, refers to the basic aspects of vision (visual acuity, etc.) are complete but still does not recognize the visual information. Central hemiachromatopsia arises when a lesion in inferior occipital cortex diminishes or abolishes color vision in the contralateral hemifield. Impairment of angular gyrus and occipital lateral gyrus results in alexia without agraphia, as do not understand the words, not through the visual way of reading text, but can through auditory, kinesthetic, tactile and other sensory pathways to achieve the purpose of understanding the text. V1 damage can lead to "blindness". Only when the object moves, can the patient perceive it, but the color and shape can not be identified. Bilateral parietal lobe damage leads to the destruction of visual attention mechanism, patients are profoundly affected by an inability to disengage and shift their attention to various parts of a visual scene. Facial recognition core network damage causes human face recognition dysfunction, patients do not even recognize their faces, but can identify individuals through other characteristics. Visual cortex and midbrain damage can also lead to hallucinations. Further study and continuous improvement of bionic eye make it reality for blind to see light again.