Atheists don't experience god/s, the blind don't experience light. Is the experience of god ... or light ... necessary to the human experience? Without either experience, is a person less human, less knowledgable? Is it possible that without the common experience of other people, atheists ... or the blind ... might know something that others don't?

Or is it, that as in essence whiteness is not so much a color as the visible absence of color, and at the same time the concrete of all colors; is it for these reasons that there is such a dumb blankness, full of meaning, in a wide landscape of snow--a colorless, all-color of atheism from which we shrink?
-- Herman Melville, Moby Dick 1851

Sight, Blindness ... and atheism

Human Eye is Reported to Set Clock for the Body

Boston researchers have demonstrated for the first time that the human eye has two functions, one of which is independent of its ability to see.

Just as the human ear controls both hearing and balance, the eye, these researchers showed, not only permits conscious vision but also independently registers light impulses that regulate the body's internal daily clock. Even people who are totally blind and have no perception of light can have normal hormonal responses to bright light, the researchers found.

Put another way, there are two distinct visual systems in mammals, or as one expert said, the human eye can have vision without sight.

The finding, reported today in The New England Journal of Medicine, is of more than academic interest, and could lead to changes in the ways blind people are treated. The head of the research team, Dr. Charles A. Czeisler, said in an interview yesterday that it is common practice to remove the eyes of people who are totally blind and provide them with cosmetically more pleasing artificial eyes.

It is also commonplace for totally blind people to go for years, even decades, without undergoing an eye examination that might pick up treatable conditions like glaucoma that block the ability of the retina to register light.

The result of both practices, Dr. Czeisler said, is that most of these people lose the ability to regulate their biological clocks to the 24-hour cycle of day and night. This typically causes a debilitating, life-long sleep disorder that mimics jet lag. Without the influence of light, the body's internal rhythm runs slightly longer than 24 hours. Gradually the natural sleep-wake cycle of these people get more and more out of line with day and night.

Dr. Czeisler, an endocrinologist and specialist in sleep disorders and circadian rhythms at Harvard Medical School and Brigham and Women's Hospital, said that some blind people are able to remain synchronized to an ordinary 24-hour day even though they have no conscious perception of light. It had long been assumed that their ability to adapt to a normal circadian rhythm was the result of physical activities and social cues, which also help sighted people adjust their sleep cycles to a 24-hour day.

But in sighted people the primary mechanism for keeping the circadian clock synchronized with day and night is the input of light through the eyes. This light passes through the retina and travels through a special tract in the optic nerves to a region of the brain called the suprachiasmatic nucleus, the brain's pacemaker.

The light impulses then go on to the pineal gland, stopping to release a hormone called melatonin. Melatonin, the so-called hormone of darkness, normally reaches a peak in the blood at night when the lights are out. But when bright light is shone in the eyes, melatonin production shuts down.

Dr. Czeisler an his colleagues tested 11 totally blind men and women and 6 men with normal vision. Even though the blind people had no conscious perception of light, melatonin production shut off in three of them when they were exposed to bright light at the peak of melatonin release.

"We were amazed to find that one-third of the blind people responded normally to bright light," Dr. Czeisler said. "And all three who responded in this way also had been synchronized to a normal day."

In an accompanying editorial, Dr. Robert Y. Moore of the University of Pittsburgh noted that "the importance of this type of vision is emphasized by the situation of the other blind subjects, in whom it has been lost."

"Not only can they not perceive the visual world," Dr. Moore wrote, "but they also cannot synchronize their lives to it. Their eyes are bad, and so their whole bodies are in darkness."

Six of the remaining eight blind people tested showed no response to the bright light and had circadian rhythms that were chronically out of whack with day and night. The other two were synchronized to day and night but had a long-standing history of insomnia, suggesting that other factors influencing their internal pacemakers did not always function well.