The absence of cones, the retina is not damaged, and achromatopsia can also have excellent acuity. Transient achromatopsia which is a temporary loss of color vision caused by short-term vascular insufficiency, apparently around V1 and V2 in the occipital cortex. Many people with strokes or mild brain infections have shown temporary loss of color vision. Chromatopsies are more common as a color distortion than an outright deficiency. Chromatopsia patients simply do not perceive certain colors as well as others. Phantom chromatopsia is a rare disease that affects patients who are blind or nearly blind..