Scientists also research the causes behind near-death and out-of-body experiences. The scene has been described many times: a patient in a hospital reports a floating sensation, seeing a dark tunnel and a bright light, and being able to look down on his own body from above. Part of the mechanism that causes such sensations can come from heart failure and oxygen starvation in the brain. These conditions cause the pupils to widen which causes the patient to see bright light and also perceive objects in his peripheral vision as blurry. Consider going to the eye doctor and getting eye drops that make your pupils widen. Your vision will get blurry. I, for one, often needed to have my mom read me the book I brought to stave off boredom in the waiting room.
The dark part of the tunnel experience occurs due to lack of blood flow to the eyes. The first thing to go during oxygen starvation is sight. Many people have experienced this while fainting. First their vision starts to fade out, followed by their hearing, and then their consciousness. Additionally, the way blood flows through the eyes means that the edges of the retina start to fail before the center, hence tunnel vision. As a result, tunnel vision is reported most often in cases involving oxygen starvation and not during other near-death experiences.
Floating, flying, and travelling sensations can be caused by the effects of oxygen starvation on muscle fibers. They may send incorrect signals to the brain, the brain may make mistakes interpreting these signals, and the patient may be convulsing. The involuntary movement and inability to interpret stimuli accurately lead to a feeling of motion. The sensation of seeing a bright light at the end of a dark tunnel and then watching that light get bigger as the pupils widen can also evoke motion.
