Category 4 sunglasses

As a pilot I am always considering what is the correct darkness (density) of sunglass lenses is correct for my flying conditions.

General purpose sunglass lenses will have VLT (Visible Light Transmittance) values of between 15 and 20%.

VLT is the amount of light the lens tint allows to reach your eyes.

 But that much light may be too much for some people. For example, people with blue eyes may have a higher sensitivity to light and require a darker tint in their sunglasses.

If you have extra sensitive eyes you might need to go down to 8% VLT, or even less.

Another factor is age. As we age our eyes gradually lose their "light gathering ability", especially after the age of 50 or so.

Light transmission percentage sunglasses

In that case higher VLT lenses of 20-30% or even lighter may be appropriate.

Selecting a lens with the correct VLT is the first step. It is also important to select lenses that effectively block UV (ultraviolet) light as well.

Since UV light is one of the causes of cataracts, the lenses should block most of the UV light.

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