There are no government regulations on the amount of UVR that sunglasses must block. Sunglasses are regulated as medical devices by the FDA and may be labeled as UV protective if they meet certain standards. Parents should look for a label that states that the lenses block at least 99% of UVA and 99% of UVB rays.
Protection is provided by a chemical coating applied to the lenses. Lens color has nothing to do with UV protection. Ski goggles and contact lenses with UV protection also are recommended. It is never too early for a child, even an infant, to wear sunglasses. Larger lenses, well-fitted and close to the surface of the eye, provide the best protection.
Source: Pediatric Environmental Health, 3rd Edition (Copyright © American Academy of Pediatrics 2011)