[Measurement set-up for estimation of colour discrimination thresholds of colour vision deficiencies and while wearing coloured filters].
BACKGROUND
In clinical practice, several techniques for the evaluation of colour vision deficiencies are well established. Most of them are designed for the detection of congenital or pathological changes. Due to the narrow-banded light sources, used in monitors or anomaloscopes, the human gamut can be addressed only in part. With these set-ups, the impact of coloured filters on colour vision such as blue light filtering intraocular lenses cannot be investigated precisely.


METHODS
The technique is based on the visual matching of colour differences between two halves of a test field. The colours are generated by mixing seven types of LEDs. A transparent, vertically divided circular test field is retro-illuminated with this light using optical fibres and projection optics. An ocular optic assures the unaccommodated sight of the subject on the test field (size 2 degrees).


RESULTS
The developed set-up presents freely adjustable colours in the form of continuous light spectra to examine the influence of filter materials on colour discrimination. A colour space can be generated which corresponds to that of human perception. The saturation and brightness of the light is adjustable. The subject has to decide if he can discriminate between the colours in the test field halves or not. Before the next colours are shown the subject is neutrally adapted by a neutral hue to provide different adaptation levels. The luminescence of the test field can be varied up to 1500 cd/m(2). The adaptive algorithm of the sequence is based on the SIAM method described by Kaernbach. Based on reference measurements, including 4 subjects with a congenital deficiency, it was shown that the discrimination thresholds at the characteristic confusing axes are significantly different than those with normal colour vision. Also, the impact of green laser goggles on the colour perception was determined. Due to the filter the thresholds in the vicinity of yellow (x = 0.4664; y = 0.4525) are reduced in the yellow-orange and cyan range and increased in the green-yellow and magenta range.


CONCLUSIONS
With this set-up an objective instrument is available for clinical research in the field of individual human colour perception. It enables an accurate and detailed analysis of the impact of coloured filters as well as a quantitative detection of congenital anomalies. The adaptive algorithm allows short sequences and precise determination of colour discrimination thresholds.
Schürer
M
M
Medizinische Optik am Institut für Medizinische Physik, Universität Erlangen-Nürnberg. michael.schuerer@imp.unierlangen.de
Walter
A
A
Eppig
T
T
Brünner
H
H
Langenbucher
A
A
D003119:Color Perception Tests / Q000295:instrumentation* / Q000379:methods; D055253:Color Vision; D003117:Color Vision Defects / Q000175:diagnosis* / Q000503:physiopathology*; D003124:Colorimetry / Q000295:instrumentation* / Q000379:methods; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005139:Eyeglasses; D005374:Filtration / Q000295:instrumentation* / Q000379:methods; D006801:Humans; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012684:Sensory Thresholds