Do deviations from radiance-invariance of metameric matches contradict the three pigment theory of foveal trichromacy?

According to the pigment theory of matching, metameric matches result from the equation of the rates of photoisomerizations for each of the three classes of cone pigments excited by the two matched fields. If true, matches are radiance-invariant and additive. Tests of the theory in this paper show small but ubiquitous failures in radiance-invariance due to systematic rather than random errors in matching. A choice between two possible explanations for these systematic errors favors the view that in subjects who deliberately or intuitively search for the middle of the matching range, the errors are due to an asymmetry in the Weber fraction for color (Trezona) at low (but not high) levels of retinal illuminance.

The change in the neutral point of dichromats with change in the angle of incidence of monochromatic light on the retina.

The hypothesis was tested that the change in the perceived color of monochromatic light with change in its angle of incidence on the retina can be accounted for completely by prereceptor factors alone. This was evaluated by measuring the change in the match of a monochromatic light to a fixed (and normally incident) white light as the monochromatic beam changed its traverse through the eye from chief ray to "off-axis" retina incidence at the margin of the exit pupil. Two protanopes and four deuteranopes were tested. In each case, the wavelength of the chief ray at the match was consistently, reliably, and (statistically) significantly larger than that of the match with the "off-axis" beam. The result cannot be accounted for by prereceptor factors alone.

Detection of abnormal haemoglobin by capillary electrophoresis and structural identification.

Haemoglobin obtained from a male adult Ghanian with retinopathy, which was probably caused by haemoglobinopathy was analysed by capillary electrophoresis (CE) for clinical diagnosis. Two major peaks, which were in the ratio of nearly one, were detected. The elution times of these peaks (HbXI and HbXII) were faster than that of normal haemoglobin (HbA). The existence of two different abnormal types of haemoglobin was clear in the patient blood. The following sequence analysis revealed that the first peak (HbXI) was HbC and the second (HbXII) was HbS on the electropherogram, and that the patient was a heterozygote of HbS and HbC (HbSC disease). One of the diagnostic processes in a haemoglobin disease was shown by the combined use of CE, HPLC and a protein sequencer.