During cycling, sunlight comes from every angle one can imagine. Most prescription mountain biking glasses are usually wrap around so that they can provide maximum protection from UV rays’ penetration.
Usually, UV protection is one of the most important features when purchasing the best mountain biking sunglasses. Scientifically, UVA rays penetrate deep into the dermis, which is the skin's thickest layer. Unprotected exposure can lead to premature skin aging and wrinkling (photo-aging), and suppression of the immune system. Usually, UVB rays burn the superficial layers of the skin. It plays a key role in the development of skin cancer. Even though weak, UVC can cause Erythema.
Apart from wrapping around the face, the best sunglasses for mountain biking should be certified category 3 and 4. Category 3 & 4 mountain biking sunglasses offer 100% protection against UVA and UVB radiation.