What causes blacking out or blurred vision?

Blurred vision or blacking out in front of the eyes may be caused by various factors, including the following: 1. Postural changes: Suddenly standing up from a lying or squatting position may cause blood to flow toward the waist and abdomen, potentially leading to temporary cerebral hypoperfusion and resulting in blurred or darkened vision. 2. Intense physical exercise: After vigorous activity, the body's oxygen demand increases, and the heart may temporarily fail to pump enough blood, causing insufficient cerebral blood supply and visual darkening. 3. Pathological causes: Malnutrition—prolonged starvation may lead to anemia or hypoglycemia, resulting in inadequate blood supply to the brain and eyes, thereby causing visual darkening. 4. Heart diseases: Conditions such as arrhythmia, obstructive cardiomyopathy, and aortic valve stenosis may impair cardiac function, leading to reduced cerebral perfusion. 5. Cerebrovascular diseases: Carotid artery stenosis or vertebral artery stenosis may result in insufficient arterial blood supply and ocular ischemia, manifesting as visual darkening.