I recently bought a pair of Gascan Sunglasses and I noticed that where the glasses sit on the nose via the bridges, they are made out of smooth plastic.

This then leads to the glasses sliding down the nose and off the face, it also means I cannot tilt my head downwards and also even when looking straight or slightly upwards I have to keep pushing them back to the top of my nose where they should stay.

Is there a solution to this problem?

Maybe you can give it back to the store and replace it with another one..

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I really love my Prada Sunglasses and Diesel Sunglasses.. I also love my Adidas Ski Goggles. They are really cool

I don't think your glasses are broken, I know a lot of people who have trouble wearing sunglasses without nose pads. There is a smaller version of Gascans available, you should see if you could trade yours in for the small version. The smaller sunglasses fit a bit more snug on the sides and don't slide off my face like the larger ones do. I don't know if you have the same type of face I do, but the smaller ones were a perfect fit for me. The style is very slightly different, there is a little piece missing where the earpiece meets the lens, you'll see right away when you hold them side by side.

I have always preferred Oakley sunglasses, their lenses are of excellent quality.