English: Illustration of the visual phenomena accompanying a grey-out loss of consciousness. In the left image, the patient sees the world normally. Center depicts the onset of the grey-out, where the world appears to lose contrast, often accompanied by auditory phenomena. In the right image, the world has vanished into grey except for a small "tunnel" in the center of the patient's visual field, but even there bright lights appear dim. Subsequently, the patient typically loses consciousness. Because these visual effects occur only to the patient, they cannot be photographed, and are simulated here. The patient (and artist) briefly lost consciousness while donating blood.