Dizziness, pre-syncopal
Some symptoms of dizziness such as wooziness, feeling about to black out, and tunnel vision may be pre-syncopal and are due to insufficient blood flow to the brain.
These symptoms are typically worse when standing, improve with lying down and may be experienced by healthy individuals who rise quickly from a chair, often after a meal, and have a few seconds of disorientation.
See also: Syncope