Scientifically, supposedly a visual artefact due to the light fatigue in your eyes, this is nonetheless a way to look back into history, for this might surely be linked to the beginning of fire mastering by humankind. This, is the hypothesis here, for both may be correlated with a link of causality, meaning that ancient people night-gazing at fire may have seen this visual phenomenon to later build the amulet (or passing on its description to build it, believing it could protect them).
This is an exclusively personal demonstration to observe, which could amaze you in a kind time-machine feeling, while imagining what could have been the nights and stories behind this sight.
This experiment is reproducible with no cost (a candle, a lighter and a dark place or at night).
From Wikipedia the Nazar eye dates back from the 16th century BC to the 5th millennium BC.