Theyr are not quantified measures of any optical quality standard. Neither term equates to Optical Class One .
Optical class is a rating to determine the optical quality of a lens.
The lens should be free of blemishes, waves, or other distortions, and should be equal in color and absorptive qualities across the lens and from the left eye to the right. Though slight imperfections are hard to detect immediately, if there are any inconsistencies in these areas you may eventually have eyestrain and develop a headache. These distortions can also affect your performance in critical tasks in your workplace or sport. Our TruSphere lens technology enables us to form lightweight shatterproof optical Lexan into a sphere with perfectly consistent lens characteristics throughout. Shields are guaranteed to be Optical Class One.