Dame Judi Dench has said she is driven "spare" by people asking when she is retiring.
The 79-year-old, who was diagnosed with macular degeneration which can lead to blindness several years ago, can no longer read her own scripts.
Dame Judi, who is appearing alongside Dustin Hoffman in a BBC adaptation of Roald Dahl's Esio Trot this Christmas, said age is "just a number".
Speaking at a screening of the show in central London, she said: "It drives me absolutely spare when people say 'Are you going to retire?' or 'Don't you think it's time you put your feet up?' or tell me my age.
"I loathe it. I don't want to be told that I'm too old to do something; I want to try it first and then, if I don't succeed, then I can be told I can't do it.
"Otherwise, because you get to a certain age, it's 'Oh well, you mustn't do that because you might have a fall or you can't learn the lines or you can't see'.
"Let me have a go. Let us all have a go."
Dustin plays retired bachelor Mr Hoppy, who is secretly in love with his neighbour, Mrs Silver, played by Dame Judi, who lavishes all her affection on her pet tortoise Alfie in the one-off adaptation by Richard Curtis.
The film-maker, whose hits include Four Weddings And A Funeral and Notting Hill, said he thought the pair of elderly lovers in the story were the "couple most likely to stay together" out of all the characters in his films.