Key features of glacier sunglasses
In the mountains, the impact of sunlight is much higher than in the plains; its rays are filtered less by the atmosphere. The amount of UV light increases by 4% for every 300 m of elevation. Snow reflects 85% of UV (80 times more than grass and 4 times more than water). Infrared light also starts becoming harmful above 3,500 m of altitude, another reason why proper eye protection is crucial.
Category 4 lenses:
Category 4 protection is imperative in mountain or high-mountain areas with glaciers or snow. In medium mountain altitudes without snow or on cloudy days, category 3 protection is sufficient.
Some useful tips
Sunglasses appropriate for glacier or high mountain environments must be equipped with category 4 polycarbonate or mineral glass lenses in brown tint (for improved depth perception) with a mirror flash coating (for better protection from reflected rays). Side shields and nose guards are essential to meet the extreme conditions of this sport.
Since July 1995, a European standard requires manufacturers with CE labelling to indicate the manufacturer’s name and the filter category. This scale indicates the filtering of visible light but does not in any way indicate protection from UV (Ultra-Violet) and IR (Infrared) light.
In France, products sold must protect 100% from UV light.
- 0: transmits 80 to 100% of the light
- 1: transmits 43 to 80% of the light
- 2: transmits 18 to 43% of the light
- 3: transmits 8 to 18% of the light
- 4: transmits 3 to 8% of the light