At airports around the world, certain international travelers frequently cross borders without passports. They rely instead on a new security system that confirms their identity by looking into their eyes. These iris recognition systems are already proving effective at London's Heathrow Airport and Amsterdam's Airport Schiphol, and they are scheduled for installation this year at 11 Canadian hubs.

Not to be confused with retinal scanning, which focuses on the pattern of blood vessels in the back of the eye, iris identification works by noting the distribution of distinguishable characteristics-striations, pits, filaments, rings, freckles, and darkened areas-within the eye's colored membrane. The systems examine the iris with infrared light that reduces reflections and penetrates glasses and contact lenses, preventing such eyewear from interfering with recognition. The technology was first studied in the 1930s, and thanks to algorithms developed by John Daugman, a computer scientist at the University of Cambridge in England, it became feasible in the 1990s. Iridian Technologies in Moorestown, NJ, owner of Daugman's patents, licenses them to such companies as IBM, Panasonic, and EyeTicket in McLean, VA.

Iris identification is highly accurate. The technology measures more than 250 distinct features. Fingerprint analysis, by comparison, usually captures 40 to 60. In 2001 the National Physical Laboratory, the U.K. standards lab, used Daugman's algorithms to compare more than two million samples. The iris system produced no false matches, establishing its superiority to all other biometric systems on the market. And because no two irises have yet been shown to be identical, the chance is about one in a million that a person would be mistakenly identified, according to Iridian Technologies.

When it comes to biometric security, one might say, the eyes have it.