how much harmful blue light is blocked by prevencia?
<answer> 20 percent harmful blue light is blocked by prevencia. <context> Crizal Prevencia No-Glare Lenses by Essilor. Crizal Prevencia lenses, developed by Essilor, incorporate a proprietary blue light filtering lens technology called Light Scan which deflects harmful blue violet light by 20 percent allowing blue turquoise light to pass.