Ultraviolet (UV) treatment:

Just as you use sunscreen to keep the sun's UV rays from harming your skin, UV treatment in eyeglass lenses block those same rays from damaging your eyes. Overexposure to=2 0ultraviolet light is thought to be a cause of cataracts, retinal damage, dry eyes and other eye problems. High index and Polycarbonate lenses have 100% UV protection built-in. But with regular plastic lenses, a lens treatment is required for these lenses to block all UV rays. This UV treatment does not change the appearance of the lenses and is quite inexpensive.