Spring has lengthened the days in the Northern Hemisphere, but south of the equator, winter-and the attendant gloom-will soon arrive. In Buenos Aires and Cape Town, sufferers from seasonal affective disorder (SAD) are feeling the lethargy, food cravings and depression that result from their brains' failure to shut down production of the nighttime hormone melatonin. There is a physician-tested remedy for the "winter blues": an hour of exposure to bright light each morning. Many SAD patients use $300 tabletop light boxes. But they may eventually may be able to get their dose of summer light on the subway or at work. Enlightened Technologies Associates, a Fairfax, Va.-based startup, has rigged a pair of glasses with a battery, LED and fiber optics to deliver light directly into the pupil. Because the light enters at an angle, the user still sees normally. Tests are under way for treating SAD, sleep disorders (especially among the elderly) and jet lag.