What are they? Top of the range shades.

In what way? Price, for a start. And technology.

The technology first. Methods developed at Nasa for protecting lenses in space: it's compared to using a graphic equaliser for sound waves. Blue light is selectively reduced.

So what? You get better clarity and less blurring. Revos cut out infra-red frequencies as well as ultra-violet, and the lenses have 25 anti-glare coatings.

And the price? Between £70 and £160.

Who wears them? The Red Arrows aerobatics team. David Hempleman-Adams took a pair to the North Pole.

So what happened to Ray-Bans? Still the biggest: they sell 20 times more than Revo's 20,000 a year in the UK and hold 30% of the £50-plus market.

Where do I get them? Phone Luxottica on 020-8830 0066 for local stockists. Also Sunglass Hut, opticians, department stores.

But I'm poor: Anything with British Standard 1836:1997 gives the all-important protection against ultra-violet light. You can get them for as little as £15-20. Impartial information about sunglasses from the Eyecare Information Service (01673 857847, www. eyecare information-service. org.uk).

What's the alternative? Risk of cateracts, snowblindness, crow's feet, loss of street cred.