第2色盲の色感覚と色識別能力

Perception and discrimination of color by deuteranopes

　先天性片眼第2色盲を色名呼称法で検査し，左右眼の結果を比較することにより，第2色盲生来の色感覚を正常者の色名で表現した．またこれを一般の第2色盲の色名呼称と比較して，彼らの色感覚と色名との対応関係を検討した．

　第2色盲には本来青紫と緑の感覚は存在しない．しかし正常者が赤を感じるのと同じ範囲に，波長依存性に増加する成分—赤類似感覚—が存在する．一方学習によって，非常に不飽和な青または黄の感覚を識別して緑と呼称することが可能となる．黄味緑から黄・橙・赤の色識別は明確ではないが，長波長側には赤成分が存在し，この領域が同一色相ではないことは明らかである．

　二色型色覚者は青と黄の2種類の色しか知覚できないとした定説は誤りである．また色覚異常者では色感覚と色識別能力とは明確に区別する必要があり，後者は成長につれて向上する．

A 27-year-old female was diagnosed as uni-lateral deuteranopia in her right eye. With her cooperation, we tried to translate the color percep-tion by bilateral deuteranopes into the hue vocabu-lary of the normal. The results were compared with those of a 25-year-old male who was bilateral deuteranope and was a post-graduate majoring in color psychology.

In deuteranopia, sensation of purple-blue and green is totally absent. A component, different from yellow, exists over the range which is per-ceived as red by normals. This component varies as a function of wavelength.

Deuteranopes learn, on the other hand, to match their sensation of desaturated blue or yellow withgreen of the normal by training. They thus succeed to call these colors as green almost correctly. Although they cannot discriminate accurately the spectral locus between yellowish green and red, the red component increases with wavelength depen-dence in the long spectral wave range. It is there-fore clear that this locas is not isochromatic for dichromats.

The theory that dichromats have only two color perceptions, blue and yellow, does not seem correct. Color perception and the ability of color discrimina-tion should be strictly distinguished, particularly for color-defective subjects. The latter ability also improves with advance of age.

Rinsho Ganka (Jpn J Clin Ophthalmol) 41(19) : 1183-1186,1987