Digging out my dusty old opticians hat for a bit.
Please make sure your sunglasses are marked with a CE or BS marking (BS EN 1836:2005) to show they protect your eyes from harmful UV. Many cheaper fashion sunglasses do not have this marking and so will not protect your eyes.
It is not about how dark the tint is, a dark tint with inadequate UV filtering will cause the iris of the eye to open up and allow more UV to enter the eye than without the lens.
Sunglasses tints are also catorgised as Zero - 4 according to their light transmission.
Zero being a "clear" untinted lens passing 80% - 99% of light to the eye.
2 & 3 both being acceptable for day time driving only.
4 being "very dark" passing only 3% to 8% of light to the eye, these are classified as "Not for day or night driving"
I hope this is helpful / of interest, I'll put the hat away now.
That's useful info David. What is your opinion about polarization v just a dark lense?
Nick
