Temporary chromatopsia and alternate umbropsia in multiple sclerosis.

Uncommon visual symptoms were described in two women with clinically definite, remittent multiple sclerosis. In the first case with right optic atrophy temporary chromatopsia (vision of only blue colour) and left-sided, paroxysmal and alternate "fading out" followed by "brightening up" vision (umbropsia) occurred spontaneously. In the second case with bilateral optic atrophy transient chromatopsia (vision of only green colour) and short-lived "fading out" vision when fixating on a target were noted. Chromatopsia might be associated with impaired function of selected optic nerve fibers conducting impulses from a limited population of retinal ganglion cells. Alternate umbropsia and short-lived "fading out" vision probably depend on paroxysmal, frequency-related intermittent conduction block at the level of optic nerve fibers or synaptic elements.