There was an extremely uncomfortable and awkward spot for my friend in a 2004 City Championship in Iowa when a visually impaired person played a Poké Ball trainer card against my friend.
"Potion," he declared, removing two damage counters from his active Pokémon.
"That's a Poké Ball," my friend interrupted. His opponent became angry and started yelling at him, insisting it was a Potion. His opponent became so irate as my friend objected that he just let the kid play it as a potion.
If you don't believe me, ask Alex Brosseau, who was also at this tournament.
It seemed silly to me that someone who could not read cards well enough to identify them would choose to play a game where you are required to stare at the table and a handful of cards. I've also seen a hearing impaired person continue playing his turn at Nationals because he didn't hear time being called.