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We are often asked about the Category of lenses used for sunglasses and eyewear – what do they mean. The categories range from 0 to 4 with each one covering a range of VLT (visible light transmission – basically how much light the lens lets through).

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The vast majority of sunglasses are Category 3 and these have a VLT range of 8 – 17%. Blocking over 80% of light coming through makes them suitable for use in strong sun and for everyday recreational sunglasses.

Lighter lenses with high VLT (Cat. 0 & Cat. 1) will be used in low, dull and poor light conditions and for specific sports like clay target shooting.

Category 4 lenses are very dark, letting 8% or less of light – they are typically used at high altitude where glare can be intense with a high risk of photokeratitis (snow blindness). They are also suitable for eyes that are sensitive to light, a fairly common condition known as Photophobia. As the chart shows they should never be used for driving - they are too dark and therefore potentially dangerous. View our range of Category 4 sunglasses.