Comparison of the transmittance and coloration requirements of the four national sunglass standards.
There are four national standards on nonprescription sunglasses and two international draft standards at different levels of development and activity. The variation in test specifications and pass/fail criteria among the national standards makes comparisons difficult and agreement on international standards slow. Arguments about the relative stringency of standards may be, as a consequence, ill-informed and self-defeating. In this study I compared the requirements of the four national sunglass standards and then the compliance of 253 sunglass and fashion spectacle lenses with the standards in the erythemal ultraviolet (UV), near UV, luminous transmittance, and coloration. The methods and criteria of the four standards vary quite substantially but the lenses failing to comply are frequently the same. The differences and similarities among the standards are clearly demonstrated. In the erythemal UV, the standards form two pairs in their stringency (Australian and British Standards as against German and U.S. Standards). In the near UV, the British Standard stands out as being more stringent. In the luminous transmittance region there is a basic agreement. In coloration requirements, even though there is extreme variation of methods, these too provide very similar results. The U.S. requirements on signal transmittance do not serve a useful function. Some comments on the differences in labeling requirements are made.