V Viliunas¹, R Lukauskiene²
¹Vilnius University, Informatics, Vilnius, Lithuania; ²Kaunas Medical University Clinic, Neurosurgical, Kaunas, Lithuania
Background. A computerized test for identification of color thresholds has been created.
Methods. 2 prosopagnostic patients with low vision and homonymous hemianopia of visual field and 50 age matched healthy persons were tested. During the test , the observers were shown a computer generated stimulus. The stimulus consisted of a line surrounded by a grey background 2 degree in diameter. The colour saturation of line varied by increasing or decreasing its red, green, or blue phosphor luminance starting from the initial grey of the background. The brightness of the grey background was increased or decreased from its initial brightness towards the brightness of the line. Simultaneously the orientation of the line was randomly varied between horizontal and vertical. The observers were asked to judge the orientation of the line. The saturation threshold was established when the observer was not able to accurately detect the orientation.
Results. The mean of colour thresholds test was 2,6 times worse in persons with prosopagnosia than in healthy persons . It was 3,1 times worse for red colour, 2,1 for green and 2,6 times for blue colour.
The results of color thresholds test were compared with the Farnsworth - Munsell 100 Hue test results.They also showed losses of long wavelengths perception .
Conclusion. The test for identification of colours thresholds is preferable to the Farnsworth - Munsell 100 Hue test as it allows estimation of all deficiency types separately.
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