Protanomaly without darkened red is deuteranopia with rods.
The Rayleigh match, a color match between a mixture of 545+670 nm lights and 589 nm light in modern instruments, is the definitive measurement for the diagnosis of inherited red-green color defects. All trichromats, whether normal or anomalous, have a limited range of 545+670 nm mixtures they perceive to match 589 nm: a typical color-normal match range is about 50-55% of 670 nm in the mixture (deutan mode), while deuteranomals have a range that includes mixtures with less 670 nm than normal and protanomals a range that includes mixtures with more 670 nm than normal. Further, the matching luminance of the 589 nm light for deuteranomals is the same as for normals but for protanomals is below normal. An example of an unexpected Rayleigh match, therefore, is a match range above normal (typical of protanomaly) and a normal luminance setting for 589 nm (typical of deuteranomaly), a match called protanomaly "when the red end of the spectrum is not darkened" [Pickford, R.W. (1950). Three pedigrees for color blindness. Nature, 165, 182.]. In this case, Rayleigh matching does not yield a clear diagnosis. Aside from Pickford, we are aware of only one other report of a similar observer [Pokorny, J., & Smith, V. C. (1981). A variant of red-green color defect. Vision Research, 21, 311-317]; this study predated modern genetic techniques that can reveal the cone photopigment(s) in the red-green range. We recently had the opportunity to conduct genetic and psychophysical tests on such an observer. Genetic results predict he is a deuteranope. His Rayleigh match is consistent with L cones and a contribution from rods. Further, with a rod-suppressing background, his Rayleigh match is characteristic of a single L-cone photopigment (deuteranopia).
Shevell
Steven K
SK
Department of Psychology, University of Chicago, IL 60637, USA. shevell@uchicago.edu
Sun
Yang
Y
Neitz
Maureen
M
D003119:Color Perception Tests / Q000379:methods; D003117:Color Vision Defects / Q000175:diagnosis / Q000235:genetics / Q000503:physiopathology*; D006801:Humans; D008297:Male; D055355:Opsins / Q000235:genetics; D010775:Photic Stimulation / Q000379:methods; D011601:Psychophysics; D017948:Retinal Rod Photoreceptor Cells / Q000502:physiology*; D055815:Young Adult
D055355:Opsins