Schizophrenia and Other Psychotic Disorders Among the Visually Impaired

Introduction and Definition: Schizophrenia spectrum and other psychotic disorders are characterized by delusions, visual and/or auditory hallucinations, disorganized thinking and speech, abnormal motor behavior, and negative emotional symptoms. Although the cause of these disorders remains unknown, hallucinations stand out as a prominent symptom. Historically, research on visual hallucinations in blind or visually impaired individuals has been limited. This entry aims to explore the existing data concerning the relationship between vision and symptoms of psychotic disorders, with an emphasis on visual hallucinations. Current Research: Research indicates a correlation between schizophrenia and deteriorating eye health, likely stemming from prolonged visual hallucinations and the medications used to manage schizophrenia. Childhood blindness has been identified as a protective factor against psychosis, highlighting the role of glutamate receptors in the accuracy of prediction errors related to visual hallucinations. In older individuals with declining vision, Charles Bonnet syndrome stands as a notable exception, representing a cause of visual hallucinations linked to significant vision loss rather than a psychotic disorder. Implications: There are no reported cases of schizophrenia among congenitally blind individuals. However, several studies on hallucinogenic drugs, such as lysergic acid diethylamide (LSD), in congenitally blind individuals have found that, rather than experiencing visual hallucinations, they report alterations in other senses, such as touch. This suggests that congenital blindness may serve as a protective factor against schizophrenia and other psychotic disorders, whereas late-onset vision loss does not confer the same protection. Future Directions: Future efforts should prioritize destigmatizing psychotic disorders and promote more research on nonpsychotic disorders that present with visual hallucination symptoms, such as Charles Bonnet and Usher syndrome. This is particularly important given that many individuals with these disorders refrain from reporting their visual hallucinations due to fear of being misidentified as mentally ill and concerns about potential hospitalization. Targeted Interventions: Research on the origins of visual hallucinations—whether they involve the brain, the eyes, or both—suggests that targeting the serotonin-glutamate system in therapy can improve visual hallucination symptoms in schizophrenia and other psychotic disorders. Furthermore, clinical interventions that target neurocognitive assessments help to individualize treatment based on personal symptoms and neural processing.