Abstract
Purpose::
X-linked or red-green color vision deficiencies are characterized by the inability to discriminate hues easily distinguished by color normals. The most common anomalous forms arise from wavelength shifts of the absorption peak of either the L- (deuteranomaly) or M- (protanomaly) cones, which reduces the spectral separation between the two cone types. Our aim was to investigate the effect of spectral filters, specifically designed to correct for the spectral shift of the anomalous pigment, on the performance of protanomalous and deuteranomalous observers on standard color vision tests.
Methods::
14 young, males were classified according to their anomaloscopic (Rayleigh-equation) settings as protanomalous (10) or deuteranomalous (4) All had a best corrected visual acuity of 0.8 or better. Based on their performance on the commercially available Colour Vision Test (CVD, Coloryte Hungary Rt.), each was provided with a spectral "correction" filter, which was selected from a standard set of 10 filters (5 for protanomaly and 5 for deuteranomaly). Each then performed a battery of standard colour vision tests, including the Rayleigh-equation on the Oculus and a direct viewing anomaloscope, Ishihara- and AO-HRR-pseudoisochromatic plate tests, cone contrast thresholds, with the selected filter and a neutral glass filter in a random sequence.
Results::
For 3 out of 10 protanomal and 3 out of the 4 deuteranomal subjects, the Colour Vision Test was unable to recommend an appropriate "correction" filter. For the Ishihara and AO-HRR tests, results were similar with the "correction" and the neutral filter. The axis of the threshold ellipse of the color contrast thresholds in different directions in color space were similar under both conditions but with "correction" rotated relative to the "uncorrected" condition. The anomaloscope quotients were even lower in the protanomal and higher in the deuteranomal subjects, with than without the "correction" filter.
Conclusions::
Viewing through a spectral "correction" filter provides no significant improvement in the color discriminability of protanomal and deuteranomal subjects on standard color vision tests. Any observed changes were consistent with predictions from simulations of the "correction" filter effects on these tests.
Keywords: color vision • color pigments and opsins • photoreceptors: visual performance