Charles bonnet syndrome associated with age-related macular degeneration

The visual hallucinations in Charles Bonnet syndrome (CBS) are most commonly attributed to release phenomena that arise due to a paucity of sensory input to visual association areas of the cerebral cortex (Cogan's sensory deprivation theory of visual hallucinations). The authors wished to gain further insight into this mechanism behind CBS by examining a patient who experienced reversible visual hallucinations.

The authors present a 77-year-old man with a history of severe age-related macular degeneration who experienced formed and moving visual hallucinations associated with CBS shortly after a retinal pigment epithelial detachment (RPED) in his right eye. His visual acuity had been reduced to 20/400 in the right eye.

Visual acuity improved to 20/50 in the right eye after a series of Macugen injections led to RPED resolution as evidenced by optical coherence tomography and fluorescein angiography. The visual hallucinations abruptly ceased after this dramatic improvement in visual acuity.

Reestablishment of high resolution visual input leads to a dramatic and almost immediate increase in the stimulus threshold of visual cortex cells as reflected by resolution of symptoms. The subthreshold signals that reach consciousness to produce visual hallucinations in CBS are thus immediately mitigated.