Color contrast perimetry.

A method for color perimetry is proposed in which colored test objects are presented in a white surround, so that the luminance of the object and its surround are identical. The color of the test object then may be varied in its degree of saturation, while maintaining a constant luminance. A color video instrument controlled by a microcomputer is used as a tangent screen. Foveally viewed, colored test objects are adjusted initially in luminance by heterochromatic flicker photometry to match the luminance of a white background at 100 apostilb. The relative foveal scotoma for blue light requires that test objects large enough to include the perifoveal retina be used for flicker photometry of blue test objects. Due to the progressively increasing threshold for luminance contrast detection in extrafoveal retina, differences in luminance between the colored objects and the white surrounding, as the test objects are moved into the extrafoveal visual field, appear to remain subthreshold. Test object detection can thus be expected to be a perimetric measure of color contrast detection, relatively unaffected by luminance contrast detection. This strategy should simplify the use of colored objects for clinical perimetric testing and should provide a specific test of color vision in the extrafoveal visual field.