Whether slaving over a hot stove or simply stepping outside on a cold day, those who wear spectacles have long experienced the frustration of fogged-up lenses.
But such steamy moments – which usually happen when lenses are colder or warmer than the air around them – could be wiped out with the invention of non-fogging glasses.
The lenses are coated on either side with a material that is extra-attractive to water. Their inventors say this means that when condensation gathers, it becomes an invisible film rather than fog, leaving the lenses clear.
The Optifog lenses were designed by Essilor, the French firm that created the world's first varifocals in 1959.
It believes the new lenses, priced from around ?200 depending on type and prescription, will be of most benefit to cooks, sports enthusiasts such as runners and cyclists, and medics who wear face masks.
The lenses are available in single vision, varifocal and sun-lens forms. They need to be sprayed with a chemical solution every week to keep the fog-repellent surface working.
The solution costs about ?5 a bottle and around four will be needed for the two-year lifetime of the lenses, which have just gone on sale.