Summary
In this paper a case of congenital tritanopia is described. It appears that the clinical tests with the anomaloscope of Nagel and the isochromatic charts of Stilling, Ishihara and Boström fail in the identification of tritanopia. An isochromatic chart with the aid of normalized colours obtainable from the CIBA, Basel is composed.
As it was not possible to examine all the members of the family, the conclusion is drawn with due reservation that the defect of the subject obeys heredity laws which differ from those for the other known colour defects. It is probable that the grandfather on the father's side was a tritanope too.
In the blue region of the spectrum the sensitivity of the tritanopic eye is diminished, whereas for our subject the sensitivity in the red-green region is greater than for a normal subject. As the sensitivity of normal trichromates and dichromates varies greatly, we must not conclude that the sensitivity of the tritanope in the red-green region is generally super-normal. The sensitivity as a function of wavelength obtained with the aid of absolute threshold values of the dark-adapted eye from flashes of 40 minutes diameter and of 0,1 sec. shows humps at 5800 and 5300 Å. These humps, which also occur in the curve of a normal trichromat, can be reproduced by the method used.
A number of colour mixture data obtained with a trichromatic colorimeter are presented; namely, the dichromatic spectral coefficient curves in terms of the stimuli 4700 and 6600 Å, the spectral mixture curves for the equal-energy spectrum for the stimuli 4700 and 6600 Å, the proportion of the energies in ergs of the components 4700 and 6600 Å for the mixtures of the spectral colours.
The white points of 4800 and 2800° K are located in the spectrum at 5700 and 5800 Å.
A second neutral zone in the spectrum could not be obtained with certainty. The region 4800–4300 Å makes an unsaturated impression on the tritanopic observer and is perhaps obliterated by interference of the rod system.
The tritanopic observer accepts the colour equations of the normal trichromat.
The spectral colour discrimination is presented as a function of wavelength and is in the region of 4500–4800 Å far beyond the data of normal observers.
For this reason it is rather probable that the stimuli 4700 and 6600 Å activate approximately only the one or the other of the two receptor systems.
The spectral mixture curves for the equal energy spectrum mentioned above represent therefore the fundamental response curve of the “red” and “green” response systems approximately. As the deviations in the results of the various investigators on the fundamental response curves are rather large, it is not possible to draw a conclusion as to whether indeed with the tritanope one normal response system (blue) is missing the remaining two being normal.
Keywords
Monochromatic Light Absolute Threshold Sensitivity Curve Brightness Level Normal ObserverRésumé
Description d'un cas de tritanopie congénitale qui n'a pu être décelé ni à l'anomaloscope de Nagel, ni aux tableaux pseudo-isochromatiques. Avec des couleurs normalisées un tableau utilisable a pu être établi.
Il est probable que l'hérédité de la tritanopie ne répond pas aux mêmes lois que les autres types d'anomalies du sens chromatique.
Dans la partie bleue du spectre le tritanope est moins sensible que les personnes normales examinées, par contre il l'est plus dans la partie rouge-verte du spectre.
Les points neutres du spectre de 4.800 et 2.800 K° sont situés chez le tritanope à 5.700 et 5.800 Å. L'existence d'une deuxième zone neutre ne peut être affirmée.
L'examen de la sensibilité chromatique aux variations de longueur d onde a révélé des anomalies dans la région de 4.500–4.800 Å. De plus, il a été possible d'obtenir une équation avec toutes les lumières monochromatiques en se servant d'un mélange de deux couleurs, de 4.700 et 6.600 Å.
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