An eye condition or visual phenomenon, though this term is extremely rare and its precise meaning is uncertain in modern medical literature.
From Greek 'copia' (abundance) plus 'opia' (relating to vision or eye condition), suggesting something related to abundance of vision, but the exact original meaning is obscure.
This might be one of those words that existed in older medical or philosophical texts but became so specialized or outdated that it vanished from common usage—a linguistic fossil waiting to be excavated.
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