Introduction

When a patient presents with vivid visual hallucinations, a doctor probably considers common diagnoses such as delirium, dementia, psychoses, or a drug related condition. Charles Bonnet syndrome, however, is a condition characterised by visual hallucinations alongside deteriorating vision, usually in elderly people.1 The correct diagnosis of this distressing but not uncommon condition is of utmost importance, considering the serious implications of the alternative diagnoses.

Case report

Neighbours brought an 87 year old white widower—who lived alone in a flat—to the medical assessment unit of a district general hospital. They were concerned that he was becoming demented. Apparently he had reported seeing people and animals in his house—including bears and Highland cattle. He verified these statements and said he had been seeing them for the previous six weeks. He had also often seen swarms of flies and blue fish darting across the room.

He knew that these visions were not real and they didn't bother him much, but he thought he might be losing his mind. The visions lasted for minutes to hours, and the cattle used to stare at him while quietly munching away at the grass. The visions tended to occur more in the evenings before he switched on the lights.

His medical problems included chronic lymphatic leukaemia, which had been in remission for the past five years. He was registered blind and had been diagnosed as having gross bilateral macular degeneration. He had never had hallucinations before. He also had chronic obstructive airways disease and essential hypertension. He had had no other neurological illness and no mental health problems. He did not drink alcohol or smoke. He had …