Olwin

"This is for Sir Olwin. He's as blind as a weevil, so warn him not to take it all at once."

- Gaius to Merlin

Sir Olwin is a blind, elderly man who lives in the castle of Camelot. He was prescribed medicine by the court physician, Gaius. Merlin was supposed to warn Sir Olwin not to take all the medicine at once. Unfortunately, Sir Olwin drank all of the potion in one go before Merlin could remind him not to. It is uncertain what the side-effects of doing so were (The Dragon's Call).

Trivia

 * It can be assumed, based on his title, that Sir Olwin was a Knight of Camelot at some point in his life. He may have become blind while serving as a knight or naturally in old age.