Acquired central dyschromatopsia: Analysis of a case with preservation of color discrimination

It is well-known that a focal cerebral lesion may, on rare occasions, cause a selective disturbance of color vision (Critchley, 1965; Meadows, 1974). However, the roles of striate and extrastriate lesions in central abnormalities of color vision may be difficult to separate. A patient is described who had a right homonymous hemianopsia and marked dyschromatopsia in the otherwise-spared left visual field. The patient could not identify saturated colors reliably and had grossly-abnormal performance on the Farnsworth-Munsell 100-Hue test. However, chromatic contrast-sensitivity was normal and VEPs to isoluminant gratings were present. A magnetic resonance imaging (MRI) study demonstrated extensive infarction of the left occipital lobe and a small infarction of the ventromedial portion of the right occipital lobe. This case demonstrates that even with marked dyschromatopsia, sensitivity to color differences may be preserved. On the basis of this case and a review of previous cases of central disturbances of color vision, it is proposed that preservation of chromatic contrast-sensitivity reflects residual function of primary visual cortex.