At first only "creatives" dared to wear them, but now they're on everyone's noses; so-called geek glasses have experienced a real boom in popularity over the past few years. But now the trend is developing further. "Big frames are still in, but new colours and shapes look fresher and more elegant than the classic retro glasses," says Thomas Truckenbrod, president of Germany's Association of Opticians.
"With frames, the trend is turning away from thick rims and towards more delicate shapes," he continues. "Rounder frames are replacing rectangles, and glasses don't look so severe any more."
Glaudia Chestnut, a fashion consultant from the Austrian city of Salzburg, recommends that people with squarer, more prominent features should wear a rounder shape.
"That way the glasses can balance out any physical characteristics."
People with rounder faces should be aware that oval frames will emphasise the softness of their features, she adds.
Size is also important, says Chestnut. "Small people can look drowned by a large pair of frames."
In terms of colour, "soft tones are in, especially berry colours such as blue, purple and red," says Truckenbrod. Browny colours in various shades are also tending to replace black. "Frames now often have a tortoiseshell pattern."
Chestnut advises looking carefully at the way the frames shimmer: "warm" or "cool."
"Warm tones have more red in them and cool ones more blue," she says.
People with black or brown hair suit cooler tones while blonde or red-haired people are better off choosing warmer tones.
Perhaps most surprising is the trend for using more sustainable materials. "Glasses made from natural products like paper, cotton, stone and buffalo horn are totally in," says Truckenbrod.
"But recycled materials like old vinyl from old records are also being used." But these kinds of frames are usually handmade.
"Such high quality models obviously have a matching price," says Kerstin Kruschiniski, of Kuratorium Gutes Sehen, a Berlin industry body which gives advice on eyesight, glasses and contact lenses.
There are also cheaper glasses made from metal, such as titanium and carbon, or man-made materials such as acetate.
"Metal frames are more comfortable to wear because they're lighter," says Truckenbrod.
The fact that bigger frames have remained in fashion for so long is also due to practical reasons, thinks Kruschinski.
"The rims don't interrupt your field of vision and they give you a large viewing area," she says. "That's especially useful with varifocals."
So, when fashion has a practical as well as an aesthetic appeal, the chances are better that it will last longer. It also has to suit a larger number of people. "Neon colours, for example, don't suit everyone," says Kruschinski.
New colours, new materials - is that everything? Not quite, says Truckenbrod. New advances in 3D printing mean that some people are now printing their own glasses.
One advantage is that you can style them better to your own needs and wants. But eye experts say they might not always look as good - due to the layers in which they're printed, they have a slightly rougher appearance.