Drs. Ballard and McKeith Reply

To the Editor: We thank Dr. Terao for his interest in our work. We certainly agree that our data indicated that impaired visual acuity may be attributable to visual hallucinations in elderly people with dementia, although further studies are needed to test this hypothesis. There is, however, also evidence that impairments at other levels of visual processing, including visual attention (1) and the visual association cortex (2), may be important. Certainly, a controlled trial of cataract treatment or impaired visual acuity would make an important contribution to this field.

We agree that there are clear parallels between the association of visual hallucinations and visual impairment in both Alzheimer’s disease and Charles Bonnet syndrome. It has not, however, been established that Charles Bonnet syndrome is a discrete disease entity, and we would have considerable reservations about using extrapolated anecdotal treatment information as the basis for a pharmacological intervention strategy for visual hallucinations in Alzheimer’s disease. There are, for example, no placebo-controlled treatment studies with antipsychotic agents or cholinesterase inhibitors specifically examining their efficacy in patients with Alzheimer’s disease with visual hallucinations. Trials of this kind would seem to be a more urgent priority for pharmacological clinical intervention than more speculative approaches.