The Oscar-winning star told the Daily Mirror she had age-related macular degeneration (AMD) and struggled to read scripts or recognise faces.
But the 77-year-old has had some treatment and is hoping it might slow the decline in her eyesight.
AMD affects more than 600,000 Britons and last year research was published suggesting it could rise to 750,000.
Dame Judi, who is due to reprise the role of M in the 23rd James Bond film, Skyfall, told the Mirror: "I can't read scripts any more before because of the trouble with my eyes.
"And so somebody comes and reads them to me, like telling me a story."
AMD, which affects the macula at the back of the eye, is the cause of more than half of registrations for blind and partially sighted people in the UK.
She said: "I've got what my ma had, macular degeneration, which you get when you get old."
Dame Judi stars as one of a group of pensioners who move to India in her latest film The Best Exotic Marigold Hotel, which premiered in London earlier this month.
She said the worst part of the condition was not being able to see the person she was having lunch with in a restaurant.
But she said she had no plans to let it force her retirement and added: "You get used to it. I've got lenses and glasses and things and very bright light helps."
She has been chosen to narrate the film Better Living Through Chemistry, starring Sam Rockwell and Olivia Wilde as a couple engaged in an affair.
Dame Judi won a best supporting actress Oscar in 1998 for her role as Queen Elizabeth I in Shakespeare in Love but she is not expected to attend next weekend's Oscars.
Actress Dame Judi Dench has been diagnosed with a condition that can lead to blindness, she has revealed.