Interchangeable lenses are becoming a common feature on more and more goggles. Light levels can change very quickly on the mountain and the effect that has on visibility can be dramatic. Low light caused by cloud can prevent you from being able to see contours and undulations in the terrain. This makes the snow appear completely smooth, which can be very disorienting, while bright light when the cloud clears can cause glare which can also affect your vision, so having the right goggles is essential. Here we explain everything you need to know about lenses to help you make the best choice.