“Darkness, Tunnels, and Light” by G.M. Woerlee, in Skeptical Inquirer (May–June 2004), 944 Deer Dr., N.E., Albuquerque, N.M. 87122.

“I was moving very rapidly down a long, dark tunnel. I seemed to be floating. I saw faces which came and went, and which looked at me kindly, but did not communicate. I did not recognize them. As I got nearer to the end of the tunnel, I seemed to be surrounded by a wonderful warm glowing light.” So reported a woman who nearly died in childbirth. Indeed, wondrous near-death experiences such as hers have been reported for centuries, and there’s no doubt that they’re real. But are they evidence of a spiritual realm—of life after death? Woerlee, a physician and anesthesiologist who practices in Leiden, the Netherlands, thinks not.

After his interest in the subject was piqued by the 1990 film Flatliners, Woerlee read many reports of near-death experiences. In an account given in a 1926 book, for example, a woman who came close to dying in a London obstetrics hospital first saw only darkness, then what she called a “lovely brightness,” as well as “bright forms.” No one else in the room saw any of this. As Woerlee read the account, it became apparent to him that her medical condition “caused her pupils to widen. The woman was dying of heart failure, and lethal heart failure causes oxygen starvation; severe oxygen starvation causes the pupils to widen.” When that happens, a person sees bright light and, because of the reduced depth of field, sees clearly only “people upon whom the eyes are focused, while all other people are seen as bright and blurry forms.”

Oxygen starvation, which is responsible for the terminal loss of consciousness in more than 90 percent of deaths, can also cause both darkness and tunnel experiences, Woerlee learned. Because the retina requires more oxygen than the brain does, vision will fail—producing a perception of darkness—before the loss of consciousness. And because the retina’s optical center happens to have the greatest supply of blood, peripheral vision will fail—producing a tunnel experience—before total vision does.

But what about the sensations of “moving, flying, or being drawn through a tunnel toward a light or entering the light”? Oxygen starvation affects not only the brain but “the sense organs that provide the brain with most of its information about body position and movement.” Add convulsions resulting from severe oxygen starvation, and movements of the body made in the course of treatment and care, combine all this with “a total loss of vision, tunnel vision, or the effects of pupil widening,” and the result can be those strange sensations. According to Woerlee, all aspects of the near-death experiences have a physical explanation.