UV blocking and polarization are not the same. Polarized lenses have a chemical coating that blocks horizontal light waves that bounce off surfaces (the ones that cause glares and reflections) and are specifically designed to reduce light glare and eyestrain. Although they can be used anytime your child is outdoors, polarized lenses are a necessity when glare is an issue, such as during water activities, while playing outdoor sports, and in sandy and snowy environments. Note that polarized lenses don't necessarily include UV protection, so look for kids' sunglasses that provide both.