All sunglasses limit some part of the natural light that surrounds us from getting into the eye. Visible Light Transmission (VLT) is a measure of how much light gets through in general. The darker the lens the smaller the VLT, and the smaller the VLT the less light gets through. The first thing to think about when you buy sunglasses is how much dimming do you want from your lenses. The brighter your environment (beach, snowfield) the lower you want your VLT.
Stay tuned for discussions about special use lens colors, coming soon on the SkyVision blog!