They vary in size, but the largest would is probably larger than a fingernail
at arm's length.
I have had an MRI of my optic nerves, but I never went back for the results (fool).
Can you see yours on an Amlser grid? can you see through it?
I can't look directly at my spots, since they don't move and aren't at my point of focus (yet!). they behave exactly as your does, with the curtains, window etc.