Visual agnosia is a condition in which the patient is able to see objects but is unable to recognize them visually, or is unable to recognize things that he was able to recognize without difficulty not long ago, even though the patient’s vision and reasoning ability are unchanged. The patient’s identification of familiar places, things around him, various appearances and even his relatives, and sometimes colors, becomes difficult or even impossible. 1. Visuospatial agnosia Spatial agnosia is characterized by a territorial dissociation associated with visual-spatial perception disorder. Patients are unable to discern direction, do not know how to look around, and do not know how to detect with effective attention. Several visual signs that the patient can grasp are isolated and therefore a territorial structure cannot be reconstructed from these visual signs. The patient often shows the inability to get lost in the corridors of the ward, to enter someone else’s room, or even to discern directions in the room where he lives. 2. Facial anosognosia Patients with facial anosognosia often show an inability to immediately recognize people when they see them. In severe cases, they cannot even recognize their own relatives or close friends, cannot distinguish between men and women, and cannot recognize their own faces in the mirror from those of several people. 3. Color dyscrasia is a disorder in which the patient no longer recognizes the colors he used to be able to recognize perfectly. This disorder is rarely initiated by the patient, but is only discovered through specific tests. 4. Internal image processing disorder ① Visual deformation disorder refers to the patient’s abnormal perception of issues involving the size, direction, shape, position and interrelationship of objects, which may involve all the objects seen or only some aspects of the objects. ②Visual hallucinations include geometric or primitive hallucinations, figurative hallucinations, and dual personality hallucinations (also known as hallucinatory self-sightedness, where the patient sees another self).