The absence of cones, the retina is not damaged, and achromatopsia can also present excellent acuity. Transient achromatopsia which is a temporary loss of color vision caused by short-lived vascular insufficiency, apparently at V1 and V2 in the occipital cortex. It has been observed that many people who suffer from strokes or mild brain infections show a temporary loss of color vision. Chromatopsias are more common a color distortion than an actual deficiency. Patients with chromatopsia simply do not perceive certain colors as well as others. Phantom chromatopsia is a rare disease that affects blind or nearly blind patients