Charles Bonnet Syndrome (CBS) is a condition that age-related macular degeneration patients can develop that causes visual hallucinations. It is found in patients who have profound vision loss.
Researchers have offered many ideas as to why these hallucinations occur but very few have been tested until recently when researcher, David Painter, tested the theory that the hallucinations are due to over-excitability. 
Twenty-four participants took place in the study and underwent an EEG. Participants were split into three groups of eight: one group had macular degeneration with CBS; one with macular degeneration without hallucinations and one group with normal vision.
Patients who had hallucinations demonstrated a "huge visual response" in their EEG readings of cortical activity compared to those who did not have hallucinations. Mr. Painter stressed that patients suffering from these hallucinations may not require medication and should be informed that the hallucinations are not due to brain disease.
