"Sunglass lenses work by blocking a percentage of light from passing through the lens. Usually, they block most or all ultraviolet light (a major eye-health concern), and some smaller percentage of visible light. The percentage of total visible light that passes through the lens to your eye is measured as “Visible Light Transmission,” or VLT. Darker glasses have a low VLT, and lightly-tinted glasses have a high VLT." Read on... |