Screening of red-green defects of colour vision with pseudoisochromatic tests

Fifty red-green defectives and 100 normal subjects were examined with the second edition of the Boström-Kugelberg (BK II, 1972) series and the Ishihara complete edition (1976) of pseudoisochromatic plates. The results are related to those obtained with the first edition of the Boström-Kugelberg test (BK I, 1944) and the Boström test (II B, 1950) and to the classification of defects obtained with the Nagel anomaloscope. The 50 red-green defectives were originally selected by using a combination of the BK I and II B tests. The normal subjects also, passed this preliminary test, as well as an examination with the Nagel anomaloscope. In the final examinations performed under standardized conditions, three red-green defectives passed both the BK II and the BK I test, while eight defectives passed the Ishihara test. Combination of BK II or BK I test with the Ishihara test does not improve the result. Only one defective (a borderline case of protanomaly) passed the separate II B test. Normal subjects were not classified as colour defectives with any of the four pseudoisochromatic tests used. All normal subjects passed both the BK II and the Ishihara test. Classified as suspected red-green defectives (one misreading made in standardized conditions) were five normal subjects with the II B test and one normal subject with the BK I test. In the second edition of Boström-Kugelberg series, the plates numbered 3, 5, 11, 16 and 18 are clearly less effective than respective plates of the first edition. Only the plates numbered 1 and 10 have markedly improved in the second edition. Red-green defectives made on average 0.54 misreadings per plate in the BK II test as compared with respective 0.62 in BK I, 0.69 in the Ishihara and 0.56 in the II B test.