Ultraviolet (UV) light is constantly emitted by the sun.  Scientists subdivide the UV spectrum into 3 subcategories: UVA, UVB and UVC.  UVB is recognized as the dangerous part of the spectrum while UVA and UVC are most likely harmless. 
UVB rays cause sunburn and can damage the eye’s cornea, retina and lens. Combined with cold wind and snow, UVB also has the potential to cause snow blindness (photokeratitis), a temporary (1- to 4-day) but painful problem.  Also, there is some research that suggests that daily exposure to UVB in very bright sunlight over a period of many years may cause cataracts, a gradual clouding of the lens of the eye. 
UVA rays are primarily absorbed within the lens of the human eye.  There are no documented cases of UVA causing eye disorders, though this remains a much debated and researched area. The wavelength of UVC rays is closest to that of visible light, and most experts agree that they are of little concern as they are absorbed by the upper atmosphere and do not reach earth's surface. 
UV damage is cumulative over a person's lifetime, which means you should begin protecting your eyes and your children’s eyes as soon as possible.  Your wellbeing is very important to us at Numa Tactical, and all of our lenses offer 100% protection against light wavelengths up to 400nm, thereby blocking 100% of all three classes of UV rays. 

UV Light Classes, by wavelength