It took 20-20 vision to see nothing sells like specs

Dame Mary Perkins tells Paul Rodgers how special deals and stylish frames have made Specsavers an unlikely high-street star

Dame Mary Perkins adamantly denies she's the Imelda Marcos of spectacles. Unlike the former first lady of the Philippines, who had 1,060 pairs of shoes in her wardrobe by the time her husband was deposed, Dame Mary insists she has "just" four dozen eyeglasses.

On the day we meet, she's sporting a semi-rimless pair with a light-green metallic frame, fashionable letterbox lenses and broad armatures with a horizontal slit along the middle to allow just a sliver of peripheral vision. "For years I used to tell people not to choose frames with thick arms, because if you're reversing your car you'll have a blind spot," she says, tucking the Supras back into their case. "And now, what's the fashion? Thick arms," she laughs. "So what if you crash your car?"

If her personal collection is – relatively – modest, her company stash is not. "Over the past 15 years I've kept every single frame we've carried. It's all in boxes and I'm trying to find the best way to display them," says the co-founder of Specsavers, Britain's largest chain of opticians. Possibly at the V&A, I suggest, thinking that if the country's leading design museum can make room for Kylie Minogue's gold lamé hotpants, it could surely spare a rack of display cases to exhibit a few thousand snazzy frames.

At first glance, Dame Mary, 64, is an unlikely champion for the fashion industry. Her personal style is a businesslike twinset-and-pearls look (accented with a Guernsey flag pin) and her manner reminds me more of a wise elder aunty than, say, Dame Vivienne Westwood. Yet her influence has surely been more far reaching than her punk contemporary's.

The two-for-the-price-of-one deals at the heart of Specsavers' aggressive marketing campaigns have led to a revolution in eyewear, turning a once-ugly prosthetic into a must-have fashion accessory. The chain sold 18 million prescription lenses last year, all of them made – under licence from Pentax – at its three UK factories.

Glasses are no longer a sign of geekyness and are regularly worn by people with 20-20 vision. The likes of Tommy Hilfiger, Red or Dead and, in an exclusive deal signed last year, Jasper Conran now design frames. Gone are those NHS specs for children, with the springy wires that looped over the ears and dug painfully into the flesh. Or at least, they were gone for a while. "Who would have thought Harry Potter would have brought them back into fashion?" she says.

Like some early 20th-century Bolshevik, Dame Mary is already exporting her revolution. Specsavers had more than 1,000 stores in nine countries at its year-end in February, and is aiming to double that in the next four years. Its latest expansion is into New Zealand, where it plans to open 60 outlets this year. In Australia, it has been on an acquisition spree, picking up 40 outlets from Vision Centres and Vision Crest Optometrists. Turnover also crossed the £1bn mark last year, two years ahead of schedule.

The main obstacle to global growth is the structure of national markets. "What we like is where the optics model is similar to the UK's," she says. "In Italy or France or Germany, most people would go to an eye doctor to get tested, then go around the corner to buy their glasses. We prefer to have a fully qualified optometrist on the premises, owning that practice and both testing and dispensing."

Domestically, the company is still expanding, though slower than it is abroad. Dame Mary thinks it will benefit from the downturn in the economy as shoppers look for cheaper options without sacrificing style. "Our typical customer has a very similar profile to an Asda customer," she says. Already the chain has introduced a new Star range of glasses, frames and len-ses, for just £25. "We managed to hold prices for 10 years but six months ago we could see people starting to think, 'I've only got so much money in my purse.' "

She's also optimistic about the future of her digital hearing-aid stores – after five years, already the largest private providers in the country – and positively bullish about a varifocal lens, called Occupational Tailormade Multifocal, that is due to be rolled out this autumn. And despite the downturn, the company is investing in technology. It is introducing fundus cameras, a microscope that takes pictures of the retina, as standard in many of its shops.

Specsavers is Dame Mary's second chain. The first she formed with her husband, Doug, whom she met while they were studying to be optometrists at Cardiff University. Based in her home town, Bristol, it grew to 23 stores before they sold it in 1980 for a reported £2m. Soon after that, the family moved to Guernsey, where her father, also an optometrist, had retired.

"I thought I might do something different," she says. But after a spell doing charity work for the Citizens Advice Bureau, and a term studying to be an accountant ("ghastly thought"), she returned to optics.

The lure was Margaret Thatcher's plan to liberalise the business in 1984. "Before that, you could not advertise – not even an announcement in the local paper for a new shop opening. You couldn't put frames in the window with prices on them."

Many in the industry decried the reforms as the end of the small, family optician. "It was like asking turkeys to vote for Christmas," she says. But the flip- side, she realised, was that a chain could lift the burden of boring business bits so opticians could spend more of their time gazing into eyeballs.

Her vision was a chain of joint partnerships, similar to fran-chises. Most of her shops are half owned by Specsavers and half by the resident optician. The company looks after such back-office operations as marketing, payroll and the warehousing of frames at the headquarters in Guernsey, where it is the island's largest private employer.

The result is that some 1,000 opticians have survived instead of being squeezed out by chains of wholly owned shops.

The irony for Dame Mary is that all this means she no longer does eye tests herself. Instead, she contents her self with "secret shopper" expeditions, which she finds far more informative than focus groups. "You wouldn't believe the things people will tell you if you're just sitting next to them."

Entrepreneurial success has come at a price. Her children suffered when she was building her first chain, because the business had priority, she says. "When I give speeches, I always tell people not to do what I did." Still, her offspring have not disowned her. All three have gone into the family business and her son, John, became joint managing director last year. Though she's cagey about when, or even whether, she'll retire, the company clearly has an in-house succession plan. For good or ill, we can all expect to hear her catchphrase for years to come: "Should have gone to Specsavers".