Long wavelength pass filters designed for the management of color vision deficiencies

This study reports on the effectiveness of long wavelength pass filters dispensed as tinted spectacles as an aid for individuals with congenital red-green color vision deficiencies. The effectiveness of the filters was evaluated by the performance on a series of clinical color vision tests and a questionnaire after the subjects had tried the lenses for 1 week. The lenses improved performance on color vision tests that required discrimination between large color differences, particularly between red and green hues. However, performance was degraded on tests which required fine color discrimination or used colors that were located parallel to the tritan confusion axis. The improved performance on certain tests was primarily based on brightness artificats induced by the filters, whereas the degraded performance on the other tests was due to the absorption of short- to midwavelength light by the filters. A slight majority (56%) of the subjects rated the filters as being moderate to highly effective in improving their color discrimination. Nevertheless, only 17% were interested in actually purchasing a pair. Common reasons for rejecting the filters were the color distortions produced by the red filters and fewer colors were actually perceived when wearing the filters.