What does the word 'twenty-twenty' mean in English?

As per Merriam-Webster, one meaning of 'twenty-twenty' is associated with the human eye. It means "meeting a standard of normal visual acuity", for instance, "I had twenty-twenty vision". Another meaning is- "marked by facilely accurate discernment, judgement, or assessment". The idiom 'twenty-twenty hindsight' means "the full knowledge that one has about an event only after it has happened."