Suffering with hallucinations

Hi I would just like to ask if anyone else have had shadows from the corner of the eyes or hallucinating quite often. It is not there all the time but my husband seems to be seeing them more often, than he has for a while, but can’t find out a lot about it. Optitician says it could be that Parkinson’s affects the muscles of the eyes and it could be you see something out of the corner of your eye but when your eye gets there it’s gone because of the slow movement of the muscles. Have anyone heard of anything like this happening to them