Eyelid twitching is a sign of many things, but almost never any serious problems!
20/20 vision has always been considered "perfect vision" by most people. And of course we have all heard nearsighted individuals call themselves blind! But it is hard to know what '20/20 vision' means, and we all know that nearsighted people are not truly blind.
The term '20/20 vision' became known as perfect vision because eye doctors used examining rooms, known as 'lanes' that were 20 feet long! If a patient could see normal sized letters at 20 feet, this was perfect vision. If they needed letters that were twice normal size, they had 20/40 vision, meaning that they were still 20 feet from the letters, but someone with perfect vision could stand 40 feet away and still see the letters.
Blindness is defined as 20/200 vision or worse in both eyes WITH corrective lenses or contact lenses. For this reason, as long as they wear their proper correction, nearsighted patients are not truly blind!
To find out more about 20/20 vision, or about eye surgeries such as LASIK or ReLEx