Polarised lenses: The bright light reflected off surfaces like water or the windshield that makes you squint is caused by horizontal rays of light. Polarised lenses block those horizontal rays. However, polarised lenses don’t block UV rays, so make sure you pick a pair that does both.Photochromic lenses: These block ultraviolet light and protect your eyesight.
Tint: The colour or darkness of the lenses has no relation to UV protection. A dark-coloured lens is no better than a light-coloured one if there’s no UV protective coating. However, dark grey is probably best for most people because it offers the least colour distortion.
Fit: Close-fitting sunglasses will block out more harmful UV rays from the sun. They will also protect the light that sneaks in at the side of your sunglasses.
Quality: The quality and the technology used in the sunglasses plays a major role in protecting your eyes. Some sunglasses offer Spectral Control technology which is not a coating. Rather it’s molecularly engineered into the glass itself, so it will never wear off and the sunglasses will never wear out.from gulfnews.com