As early as the 1930’s researchers began to notice that the blood vessels on the back of a human eye are unique to every person. Even identical twins have different patterns of these blood vessels. In the thirties, however, there was not sufficient technology to implement these retinal characteristics into a form of advanced security. Once the correct technology was acquired, retina biometrics, one of the most sophisticated forms of security, was born. 
How it Works
Today, there are many different machines designed to perform retina scans but all follow the same basic principles. These machines require a person to take off any glasses they may be wearing and stand with their eyes very close to a scanner. The machine takes around ten seconds to shine a “low intensity coherent light source” onto the retina to illuminate the blood vessels.  The individual being scanned must remain still and stare at a specific point while the device is processing the scan. Once the machine has a copy of the scan, it compares the picture to all the different scans on file, looks for a match, and identifies the individual. 
Machine Scanning an Eye:
Example of a scanned retina:
A few advantages to Retina Biometrics include:
- No two retinas will ever be exactly alike
- Even after deceased, the blood vessels cannot be imitated since they decay rapidly
- Fast, accurate scan
Since the retina scan machines are fairly expensive, a popular use of this type of security is with government agencies to identify employees. Also, some companies (both large and small) use the retina scan machines to keep track of attendance of employees and control access areas within a building.  Since these machines are extremely accurate, they tend to be used in highly protected areas. Companies use retina scans to limit access to, usually, the top employees only. This ensures that important data will only be seen by the people with clearance. Companies also like to use these retina scanning machines since they are highly accurate in a short amount of time. Employees only have to spend around ten seconds at the machine to be granted access or denied.
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