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Measuring short-wavelength-sensitive cone discrimination thresholds using pseudoisochromatic figures displayed on a
A Watanabe1, J Pokorny, V C Smith
1Visual Sciences Center, The University of Chicago, IL, USA.
Purpose:
To simplify the testing of short-wavelength-sensitive (SWS) cone function in the clinic.
Methods:
SWS-cone discrimination thresholds were measured along the tritan axis using pseudoisochromatic figures displayed on a color monitor. A circular 6 degrees field, containing spatially discrete patches of varying sizes and luminances, was presented on a background. A subset of patches formed the target patch in the shape of a C. Eight subjects with normal color vision reported the direction of the gap in the C using a cursor controlled by a joystick.
Data:
were expressed in units of SWS-cone trolands.
Results:
SWS-cone discrimination threshold increased slowly as the SWS-cone trolands of the starting chromaticity increased. The dependence of the threshold on the SWS-cone activation level was similar to literature reports of chromatic discrimination measured with conventional paradigms.
Conclusions:
The advantages of this method: (a) It is a simple intuitive task for patients. (b) The paradigm can be implemented with an 8-bit/gun color monitor. (c) The test avoids the need to define equiluminance for the individual patient before the color test is administered. This method can provide a useful technique for measuring SWS-cone function in a clinical population.