There is no need to break the bank for that Chloé handbag. This season's hot fashion accessory isn't slung over your shoulder and needn't set you back £1,000. The new winter must-haves are sunglasses, and never mind the plummeting temperatures outside.
Some of the biggest names in the luxury world are scrambling to get a toehold in the eyewear market, which has exploded in recent years. Pucci, Jimmy Choo and Tiffany are the latest to leap into the market for the first time, vying with cult designers such as Raf Simons, House of Holland and Dries van Noten for a piece of the UK's £270m-a-year sunglasses sector.
Established brands such as Ray Ban have ridden the growing obsession for fashionable eyewear, launching eye prescription versions of their most popular designs, including the Wayfarer, as worn by Chloë Sevigny, the Olsen twins and Kirsten Dunst.
Jimmy Choo, which is transforming itself from a shoemaker into a complete accessories company, will launch its sunglasses range next January, followed by a prescription frame collection. Italy's Safilo will make the frames. Other brands poised to enter the eyewear sector or relaunch their ranges include Nicole Farhi, 3.1 Phillip Lim and the fashionista's favourite label, Balenciaga. Even Levi's has got in on the act, its new collection making its debut last week at Silmo, the eyewear trade fair in Paris.
Rachel Zoe, the celebrity stylist who kick-started the trend for giant frames hiding emaciated faces, is another with designs on the market; she is currently working on a collection.
Hannah McInnes, sunglasses buyer for Harvey Nichols, says: "Sunglasses have become the new handbags because bags have doubled in price during the past few years. So people are using sunglasses as the entry point into the fashion brand they aspire to."
Tracy Sedino, co-owner of Linda Farrow, the 1970s label that was relaunched five years ago after Farrow's son found a lost trove of original frames, agrees: "It's not just seasonal any more."
Sales of eyewear in Britain are tipped to hit £2.8bn by 2010, with the sunglasses sector estimated to reach £317m by 2011, according to the market research firm Mintel. The two big Italian glasses makers Luxottica and Safilo are cleaning up. Exports of Italian-made sunglasses surged by 19 per cent in the first half of 2007 compared with the same period the previous year.
Marcolin, the Italian glasses maker that won the licence for Tom Ford's new sunglasses range, saw its sales soar by a quarter in its first half. Maurizio Marcolin, the son of the founder, says business is booming because sunglasses, "like ice-cream, are a year-round purchase. The main season used to be spring/summer, but now you can't really tell between the seasons".
Sunglasses are such big business that Luxottica paid $2.1bn (£1.05bn) for Oakley, the classic sports sunglasses brand, earlier this year. And to get its hands on Ralph Lauren's licence, Luxottica agreed to stump up $200m in advance royalties for the following 10 years.
Gok Wan, the fashion stylist who presents Channel 4's How to Look Good Naked, says he uses sunglasses to complete an outfit. "They have become a fashion staple." He adds that sunglasses in winter are a short cut to reinventing a look, "like gloves in the summer". Wan, who is the celebrity spokesman for Specsavers, said the glut of pictures in magazines of four-eyed celebrities had helped to banish the geek factor. That and the Ugly Betty phenomenon, which started a craze for the red-rimmed frames designed by Alain Mikli and sported by America Ferrera in the hit TV show. Mikli's clients include Brad Pitt, Jack Nicholson and Bono, while other covetable glasses wearers include Liv Tyler, Mischa Barton, Angelina Jolie and David Tennant.
The strength of the market has led Selfridges in London to dedicate a wall of its luxury Wonder Room to 1,000 designer frames. Richard Peck, the managing director of David Clulow, the optician operating the boutique, says glasses wearers are investing in ever more pairs: "With four pairs of glasses you can have four different looks. You wouldn't get that by buying four pairs of shoes."
Sunglasses date back to the 19th century when polar explorers used the lenses to shield their eyes from the bright sunlight reflected from the snow. It wasn't until the 1930s, when film stars wore them as protection against the Californian sun, that they developed a mass following.