I’ve just found a description of some spectacular and fantastical hallucinations from a case of Charles Bonnet syndrome, reported in a review article on the neuroscience of this curious hallucinatory state.

It’s one of the most florid cases I’ve ever come across and the experience seems both wondrous and terrifying in equal measure:

A 73-year-old woman who lived alone presented with anxiety-provoking visual hallucinations. Inch-long black ants scurried across her kitchen floor, walls and windows. In desperation, she began spraying insecticide throughout the house. Her neighbour, whose features were seemingly masked by the insects, called an ambulance. Floating seahorses and featherless chickens joined the colonies of ants in the Emergency Department. A Roman chariot, the rider dressed in gold, flashed across the curtain several times. On the ward, tropical vines grew from the foot of her bed. A man stood with thick brown tree trunks for legs and thick green branches for arms. Nurses‚Äô heads would shrink and then expand before melting into the floor. Brightly coloured fairies carrying wands invited her for walks around the hospital grounds. She once caught herself telling them to get off a road at which point they donned diamond coats, jumped into a wooden carriage, and rode up to her bedside. Ants in the mirror were at times replaced by an elephant‚Äôs trunk blotting out half her face. Her hair in the reflection flowed with cobwebs and the basin was matted with hair and whiskers. Cobwebs spilled from her cereal bowl at breakfast. The bathroom floor was covered with water that vanished whenever she tried to mop it up. The carpet in the room would lift away from the floor, roll up in the form of a snake, and slither out the door. A little girl and boy with a black and white dog stood next to the bed, as did extraterrestrial-like beings with large domed-shaped heads and slitted black eyes. Twisted heads with grotesque faces and bulbous eyes peered out from the wall, while little red carriages, trains and push bikes disappeared into it. Further history revealed an experience of ‚Äòant‚Äô hallucinations 4 months previously but the images disappeared after 2 weeks. She did not seek medical advice at that time fearing that she might be considered ‚Äòa bit odd‚Äô. Throughout the hospital admission she was rarely free from hallucinations and would repeatedly ask for reassurance that she was ‚Äònot going mad‚Äô. Two months after discharge the hallucinations were still intrusive. She owned a small black dog but would see several dogs resembling oversized greyhounds with unusually long snouts in her daughter‚Äôs yard. A man and a goat, both wearing grey hats and overcoats, often stood beside her before wandering off together down a crooked road. She grew accustomed to seeing a baby seated on the lounge chair wearing grey clothes. It smiled but made no sounds. Caterpillars and tree frogs began joining her for the evening bath. She began to notice that distractions, such as listening to the radio and attending to household chores, dampened the hallucinations, while solitude, particularly during the evening hours, tended to heighten them. At follow-up 1 year later, she was experiencing very much the same hallucinations but was more cognisant of their unreality and less anxious as a result. The only new hallucination that had since appeared was that of a bright kaleidoscopic array which would transiently emanate from her central field of vision.

The article has another case study which is also quite spectacular, and, curiously, also features a Roman chariot.

One of the most interestingly things about Charles Bonnet syndrome is that fact that it is typically associated with the most complex hallucinations, but usually due to damage to the retina or early visual pathway.

In other words, damage to the part of the visual system which deals with the most basic aspects of vision (detecting lines, light and dark and so on) can cause the most spectacular visual distortions.

It’s not fully clear why this is, but one of the most popular theories is that visual information gathered by the initial part of the system is used to limit the interpretations made by the perceptual processes later in the stream which are focussed on working out significance and meaning.

We can see this system breaking down a bit when we see momentary ‘pictures’ in TV static or in flames, as the fuzzy input means many interpretations can be made.

However, when we’re looking at more ordered scenes, our interpretation is usually more constrained – it’s more difficult to interpret light patterns from a pencil as something else.

The theory goes that when we can’t process light patterns very successfully, owing to damage to the early visual system, the interpretation processes go wild, so hallucinations are ‘released’ and cavort unconstrained through our conscious mind.

Link to article on the neuroscience of Charles Bonnet syndrome.

Link to PubMed entry for same.