Retinal scanning analyses the layer of blood vessels at the back of the eye. Scanning involves using a low-intensity light source and an optical coupler and can read the patterns at a great level of accuracy. It does require the user to remove glasses, place their eye close to the device, and focus on a certain point. Whether the accuracy can outweigh the public discomfort is yet to be seen.
How it Works:
The user looks through a small opening in the device at a small green light. The user must keep their head still and eye focused on the light for several seconds during which time the device will verify his identity. This process takes about 10 to 15 seconds total.
There is no known way to replicate a retina, and a retina from a dead person would deteriorate too fast to be useful, so no extra precautions have been taken with retinal scans to be sure the user is a living human being.
Retina scan is actually one of the oldest biometrics as 1930's research suggested that the patterns of blood vessels on the back of the human eye were uniqueto each individual. While technology has taken more time than the theory to be usable, EyeDentify, founded in 1976, developed The Eyedentification 7.5 personal identification unit, the first retina scan device made for commercial use, in 1984. At this time, they are still the primary company for retinal scan devices though they do use resellers.
Contrary to popular public misconceptions, and reflective of what is seen in the movies, retina scan is used almost exclusively in high-end security applications. It is used for controlling access to areas or rooms in military installations, power plants, and the like that are considered high risk security areas.
Retina scan devices are probably the most accurate biometric available today. The continuity of the retinal pattern throughout life and the difficulty in fooling such a device also make it a great long-term, high-security option.
Unfortunately, the cost of the proprietary hardware as well as the inability to evolve easily with new technology make retnal scan devices a bad fit for most situations. It also has the stigma of consumer's thinking it is potentially harmful to the eye, and in general not easy to use.