Photochromic alpiner ski sunglasses with anti-fog lenses that change colour intensity automatically depending on the brightness and UV light, guaranteeing an excellent visual performance. The photochromic lens protects the eyes when out in the sun or in any weather condition. Plus the lens is treated with a special resin which removes the condensation which forms on the surface of the lens when passing from hot to cold. The sunsensor lens can change colour in only 8 seconds when passing from light to dark, and 35 seconds when passing from dark back to its light colour. The frame of the Bertoni Photochromic eyewear is in nylon so they will never change shape and are highly resistant to impacts.