Mom 81 w vascular / mixed dementia, plus closed-head injury in April-now sometimes she sees bugs that aren't there.

The "bugs" can be different shapes or sizes, and often the story changes--they were as big as her finger in one version of the story, but then they were tiny in a later version of the story. The one thing in common--the "bugs" move, but only a little. The "bugs" are sometimes associated with a feeling of dizziness, but not always. Aside from this, she is oriented to reality, time, and place. I wonder if she is having visual disturbances that she interprets as bugs. She had cataract surgery 2 years ago, but she just had a complete eye check-up by her ophthalmologist a few days ago and they said she is fine--but I forgot to mention the "bugs." Any other explanations? Has anyone experienced this?