Charles Bonnet Syndrome

Charles Bonnet Syndrome is characterized by intense visual hallucination, brought on by deterioration of vision accompanied by old age (i.e. cataracts, astigmatism, the prodding fingers of dirty grandchildren, etc). Basically, lucid, sound-minded old people (the first recorded case being Bonnet's grandfather Charles Lullin) just start seeing things. They aren't just peripheral anomalies or pattern-shifting; they are full-on level three visuals:

"Lullin’s hallucinations of “women” were neatly dressed
and coiffured ladies carrying caskets or inverted tables on
their heads, or young girls approximately 8 to 10 years old
who danced around the room dressed in yellow silks with
rose-colored ribbons, pearl collars, golden buckles, and
diamond pendants. His hallucination of a “carriage,” a
coach complete with drivers and horses, expanded in
correct proportion to the size of a house." (Current Psychiatry Reports 2005, 7:168-179)


The Journal of Psycholinguistic Research has a good article summarizing early studies and categorization of the condition, and and Psychogeriatrics has some interesting case studies. In my opinion, CBS is most interesting due to it's complete lack of other symptoms associated with dementia/senility; the afflicted are fully aware that what they see is not actually there.