Parkinson type dementia, Lewy Body, and Vascular Dementia are the three types where hallucinations are more prevalent. But diminished visual perception can occur in any dementia. Genuine visual hallucinations involve seeing things that are not present, as opposed to seeing something poorly and mistaking, misperceiving or misinterpreting what is seen. A loved one with Alzheimer's can misinterpret what they actually see because of vision changes and visual perception. Just because your loved one with Alzheimer's can not acurately describe or explain what they see doesn't mean it is a true hallucination. They can see a shadow and think it is an intruder
But these are just visual mistakes. Dad seeing relatives that were not there was a hallucination.