You may remember doing an experiment back in school where you draw a cross and a dot on a piece of paper, then slowly move the paper away from your face while staring at one of the symbols with the opposite eye. At some point the other symbol simply disappears due to your optical blind spot.
Impressive as it may be to see proof of your blind spot for the first time, what’s even more amazing is how much of your vision is actually a generated illusion and not reality.
Your eyes can only focus on a very small area of detail (about the size of the nail on your little finger held at arm’s length), and your brain simply “sketches in” much of your peripheral vision based on predictions it makes, and some extra data it collects because of saccades (the way your eyes rapidly flick back and forth, even when you try to keep them still).
For example, there are small blood vessels (capillaries) criss-crossing the surface of your retina, but because they don’t ever move your brain edits them out so they don’t interfere with your vision.
Follow the instructions from 05:30 in this video to make those blood vessels temporarily appear in your visual field: