Costly hi-tech light boxes, light visors (virtual spotlights you strap over your forehead), and dawn simulators (light boxes programmed to gradually "dawn" while you sleep) are the most commonly used tools of light therapy. Of these, the plain vanilla light boxes are the most tried and proven.

Typically, you sit about two or three feet away from one of these miniature desktop suns and, without staring at it, bask in a light that's about ten to 50 times as bright as average indoor light and comparable to sitting by a sunny window or being outdoors on a sunny or lightly overcast day.

Anywhere from ten minutes to a few hours a day of such exposure is usually all it takes to have the desired biological and therapeutic effect.

For people who have a night owl pattern - like most SAD sufferers - early morning light (even before dawn) is usually apt. For ultra larks, evening exposure usually is. For people without obvious circadian quirks, timing may not matter.

Recent evidence that sunlight exposure can gradually promote a type of blindness called macular degeneration as we grow old has cast a shadow over the long-term safety of artificial light therapy. Light therapy also often causes acute, though usually mild and transient, side effects, such as eyestrain, headaches, nausea, disturbed sleep, and overstimulation, which can take the form of nervousness, irritability, nutty euphoria, or even mania.

Most serious of all, a patient at a SAD clinic in Vienna became "overwhelmingly" suicidal, while two others actually tried to kill themselves within a week of starting light therapy. The psychiatrists there suspect light is doing what antidepressant drugs sometimes do: activating depressives before it lifts their mood, giving them the impetus to act on suicidal feelings.

Here in Winnipeg, businessman Murray Waldman thinks he has a kinder, gentler alternative to those bright white lights. The small twin towers of the Sunnex light unit that Waldman developed several years ago with daughter Suzie (a former Aquarian staffer) pump out no more light than you'll find in a well-lit room. But it's all green light - a narrow band of green to which the eye's photoreceptors are most keenly receptive. Waldman, who has a masters degree in physics and a cutting edge knowledge of light therapy, claims his most-for-the-least solution is much better tolerated by users. And he's betting it's safer too: "I think that the major benefit for most people is going to be preventing blindness, as they get older."

In one clinical trial, green light much brighter than the Sunnex puts out proved as effective as white light for SAD, unlike equally bright red light. At St. Boniface Hospital, Cornell Medical School, the Oregon Health Sciences University, and other centres, preliminary research suggests Waldman's unit can do the job too. Dr. Sonia Ancoli-Israel, a specialist in geriatric sleep disorders at the University of California in San Diego, is confident enough to have just ordered another box from Waldman to speed up her study of the units for circadianly disturbed Alzheimer's patients.

"We also have a study going on now with air traffic controllers," adds Waldman, "and I know that the American military has the unit. Supposedly they're going to do something on ships off of Alaska this winter."

Anecdotally, people have been using Sunnex units since the early nineties, often on the recommendation of their psychiatrists or clinical psychologists, who often use the units themselves. Waldman's most prominent customer is a psychiatrist who pioneered white light therapy.

Although the Sunnex units are easier on the eyes, they can be as provocative as the brighter boxes.

"You have to realize that some people are bipolar," Murray cautions. "They sometimes switch into a mania; and so they find that if they use the box for half an hour to start with they go overboard." For these super light-sensitive users, as little as five or ten minutes a day of Sunnex light has proven optimal.

Waldman's light boxes are available for rent, rent-to-own, or purchase ($529 plus shipping - $389 US) through the company's website at www.sunnexbiotech.com or by calling 1-877-7-SUNNEX.

Many companies now offer white light boxes. For $235 US, Amjo Corp (1-630-584-7117; www.amjo.biz), an Illinois company run by "a couple of homesick Canadians," sells a powerful (10,000 lux) fluorescent tabletop "Satellite Light" from Northern Light Technologies that is hum-, flicker-, UV-, and magnetic field-free (good things) and uses just a few watts of electricity thanks to its parabolic reflector. The Sunbox Company (1-800-548-3968; www.sunbox.com/), designers of the light boxes used in most of the early clinical research, also offers a range of well-appointed full-spectrum boxes ($249-$525 US), visors, and dawn simulators.

But do you really need the gizmos? Going outdoors in the daytime, spending more time next to sunny windows, or getting up close and personal with the shaded or reflected light from an ordinary lamp (as I write this, my 60-watt swing arm is hovering in front of my forehead like a visor, illuminating a research paper just under my nose - it's very bright) may be adequate for many people.

Then again, sunlight has damaging ultraviolet rays which are filtered by most light boxes. The Sunnex box goes even further, filtering most of the cumulatively eye-damaging white wavelengths. And, Waldman points out, some people only respond to light before dawn.

Still, even green-light box users have to go out into the sun sometimes, and for them, as for the rest of us, studies suggest that a generous intake of antioxidant nutrients (vitamins C and E, carotenoids, bioflavonoids, etc.) protect the eyes from the oxidative wear and tear of light, making the light cure a safer long-term proposition.

If you're thinking of trying light therapy, experts recommend you get medical clearance first, especially if you have any eye disorders.