Neurologist and author Oliver Sacks provides an enlightening explanation of hallucinations experienced by his patients, which highlights the disjunction between the visual areas of the brain and the process of going blind.
Sacks explains that such hallucinations are often unrelated to thought or experience and cannot be controlled, but tend to go unreported due to the patient's fear of being deemed insane. Oliver Sacks goes on to explain Charles Bonnet syndrome, an under-reported syndrome which affects mentally healthy individuals with deteriorating vision, and sets apart the disease and psychotic hallucinations.
As one loses the ability of vision, the visual parts of the brain become hyperactive as they are used less frequently and begin to "shoot" off randomly, creating hallucinations. Oliver Sacks goes on to explain the intricate relationship between the eyes and the brain, and the intriguing knowledge that the study of hallucinations has led scientists to conclude.