I ended up drawing a younger Twilight, mostly for headcanon purposes.  
You know how Sci-Twi wears glasses but Pony!Twi doesn’t? Basically, Twilight did need glasses, she just stubbornly refuses to wear them. Since she was a personal student to Celestia instead of in a standard school system, she could take her time to decipher blurs. And her magic ability made up for her long-distance Spellcasting(She could sense the magical energy, and aimed with that instead of sight).  
Becoming an Alicorn actually fixed her eyesight. Not purposely, though. Ascension did more than just slapping wings on her. It rewired her magic and did some minor physical transformations to accommodate Pegasus and Earth Pony magics. Pegasai have near bird-like eyesight.