The star, 88, explained that her daughter Finty Williams, 51, called her one morning and said, "It's Chris Logan's birthday and he's having a walk with [actor] Ben Whishaw in Regent's Park... please wish him happy birthday?"
The mother-of-one made the call while she was taking a bath, recalling, "I picked up my phone, and I said, ‘Chris, happy, happy …’ and I just saw these two people turn and [make shocked faces]."
"Well, it was FaceTiming them,” she confessed. “I don’t know about FaceTime. Poor Chris.”
It's likely that Dench doesn't use her phone for much more than phone calls, as she revealed earlier this year that she's lost much of her eyesight since she was diagnosed with age-related macular degeneration in 2012.
"I can't see on a film set anymore. And I can't see to read. So I can't see much," she explained in an interview. "But you know, you just deal with it. Get on. It's difficult for me if I have any length of a part. I haven't yet found a way. Because I have so many friends who will teach me the script."
- Celine Dion's Brave Battle: Singer 'Having Difficulty Walking' as She Deals With Neurological Disorder, Source Spills
- Jane Fonda Confesses She Saw Michael Jackson Naked in the '80s: 'He Was Skinny!'
- Bruce Willis' Daughter Tallulah Shares Details on Actor's New Day-to-Day While Living With Dementia: 'He Still Knows Who I Am'
"It's the most terrible shock to the system," the Oscar winner said of the condition. "Ghastly. It's terrible to be so dependent on people."
Despite the hardships, Dench said she still plans to act "as much as I can."
The British actress noted that she also has a technique when it comes to reading scripts, which she called "impossible" to do these days.
"Because I have a photographic memory, I need to find a machine that not only teaches me my lines, but also tells me where they appear on the page. I used to find it very easy to learn lines and remember them," she told The Los Angeles Times. "I could do the whole of Twelfth Night right now."
According to WebMD, 1 in 10 people will be diagnosed with age-related macular degeneration, though the condition usually doesn't lead to blindness.
Never miss a story — sign up for the OK! newsletter to stay up-to-date on the best of what OK! has to offer. It’s gossip too good to wait for!