A potential result of failing eyesight is the peculiar condition, Charles Bonnet Syndrome.
This syndrome is marked by hallucinations which can be incredibly varied. For some, the hallucinations entail some rudimentary geometric shapes whereas for others it might involve sophisticated images comprised of people.
One risk according to one of Oliver Sacks' books is that this may be confused with dementia and thus Charles Bonnet Syndrome must be considered when reported hallucinations occur within a geriatric population.
Hallucinations and neuropsychology