Colorimetric analysis of four editions of the Hardy-Rand-Rittler pseudoisochromatic tests.

At the Göttingen meeting of the International Colour Vision Society, I reported on a comparison of the second edition of the American Optical Hardy-Rand-Rittler Pseudoisochromatic plates (AO HRR) with the Richmond Products third edition of the same test and concluded that the chromaticities were exceptionally poorly matched and that the new edition was a "pale imitation of the real thing" (unpublished). This conclusion led to our abandoning a clinical trial. In 2002, Richmond Products has published a fourth edition and, in 2003, Waggoner has published a modified HRR with additional (Ishihara style) plates and the tetartan confusion figures removed. As a precursor to any clinical trial, the colors used in the plates have been measured and comparisons drawn between the four editions. While the two most recent editions much more closely resemble the original AO HRR and the chromaticities are much better aligned on the dichromatic confusion lines, the excitation purities (and therefore the degree of difficulty) of the plates are less well matched in the Richmond Products editions. In addition, there is a significant degree of metamerism in the third edition and Waggoner edition that makes variations in illuminant more critical to performance.