My Mother Is 87 And Lives By Herself In Her

My mother is 87 and lives by herself in her own home. She has started "seeing shapes and figures which she determines might harm her mostly at night. She has seen an opthamologist who sent her for an MRI on her pituitary to see if there might be a tumor. She does have macular degeneration and cataracts but these "visions" are scaring her. She was unable to go thru the MRI on 2 occassions and we don't want to traumatize her further. Could these visions be her brain not communicating with her eyes or maybe dementia? We are in the process of getting her into assisted living. I don't want her comitted for psych problems because she is reasonable and lucid in most areas. I have stayed overnight several times offering to sleep in her room and when I am there there are no "visions"