Buyers Guide | Visible Light Transmission ("VLT") in Relations to Laser Safety Glasses
Most eyewear offer protection from specific wavelengths, and allow other wavelengths in the visible light spectrum to pass through for unhindered vision. Visible Light Transmission (VLT) is the amount of light that can pass through the lens of a pair of glass. With increase in VLT, more color passes through the lens. An example of this phenomenon is distortion when wearing sunglasses to block the sun. Inexpensive sunglasses do an effective job of blocking the sun, but over-filter the light creating a darker vision. Good quality sunglasses are typically priced higher, but effectively filter out the blinding rays of the sun while maintaining the natural brightness of the surroundings.
Dielectric coated glasses are far better than polycarbonates as they have a higher VLT relative to the amount of wavelengths they block out.
It is important to note that the diversity of visible light being let through should also be a factor one should consider while shopping for glasses and goggles. Below is a simplified image of what high visible light transmission and low visible light transmission look like.