Methods for determining ultraviolet transmission of UV-blocking contact lenses

Ultraviolet (UV) transmission spectra of UV-absorbing hydrogel contact lenses have been reported in the literature. Few of these studies were done following ANSI or ISO specified procedures. These published procedures do specify an integrating sphere in the detector system and a beam size, but not other instrument settings such as slit width, spectral smoothing functions, and scan speed. This work, done with Acuvue^R and Precision UV^TM contact lenses, shows that an integrating sphere is needed to ensure the accuracy of the data. A smaller beam size than specified was required to obtain accurate spectra. A slit width larger than recommended by the spectrophotometer’s manufacturer was needed to increase precision. Spectra results were unaffected by scan speed and spectral smoothing settings.