Retinal scan

A retinal scan is a biometric technique that uses the unique patterns on a person's retina to identify them. It is not to be confused with another ocular-based technology, iris recognition.

Introduction
The human retina is a thin tissue composed of neural cells that is located in the posterior portion of the eye. Because of the complex structure of the capillaries that supply the retina with blood, each person's retina is unique. The network of blood vessels in the retina is so complex that identical twins do not even share a similar pattern.

Although retinal patterns may be altered in cases of diabetes, glaucoma, retinal degenerative disorders or cataracts, the retina typically remains unchanged from birth until death. Due to its unique and unchanging nature, the retina appears to be the most precise and reliable biometric. Advocates of retinal scanning have concluded that it is so accurate that its error rate is estimated to be only one in a million.

A biometric identifier known as a retinal scan is used to map the unique patterns of a person's retina. The blood vessels within the retina absorb light more readily than the surrounding tissue and are easily identified with appropriate lighting. A retinal scan is performed by casting an undetectable ray of low-energy infrared light into a person’s eye as they look through the scanner's eyepiece. This beam of light outlines a circular path on the retina. Because retinal blood vessels are more sensitive to light than the rest of the eye, the amount of reflection fluctuates. The results of the scan are converted to computer code and stored in a database.

History
The idea for retinal identification was first concevied by Dr. Carleton Simon and Dr. Isodore Goldstein and was published in the New York State Journal of Medicine in 1935. The idea was a little before its time, but once technology caught up, the concept for a retinal scanning device emerged in 1975. In 1976, Robert "Buzz" Hill formed a corporation named EyeDentify, Inc., and made a full-time effort to research and develop such a device. In 1978, the idea of a retinal scanner was patented, followed by a practical working prototype in 1981.

Uses
Retinal scanners are typically used for authentication and identification purposes. Retinal scanning has been utilized by several government agencies including the FBI, CIA, and NASA. However, in recent years, retinal scanning has become more commercially popular. Retinal scanning has been used in prisons, for ATM identity verification and the prevention of welfare fraud.

Some states require mandatory retinal scans for truck and bus drivers. Scan results are used by state agencies to stop incompetent drivers from obtaining licenses in numerous states in order to conceal their driving records. A controversial proposal for the use of retina scans the formation of a worker registry. Every U.S. citizen would have to undergo a retinal scan. These scans would be stored in a database and would be used to ensure that each individual is a legal resident who qualifies for employment within the United States. Opponents of this application of retinal scanning are concerned that it is a major invasion of privacy and a serious threat to personal liberties.[2]

Retinal scanning also has medical applications. Communicable illnesses such as AIDS, syphilis, malaria, chicken pox and Lyme disease as well as hereditary diseases like leukemia, lymphoma, and sickle cell anemia impact the eyes. Pregnancy also affects the eyes. Likewise, indications of chronic health conditions such as congestive heart failure, atherosclerosis, and cholesterol issues first appear in the eyes.

Pros and Cons
Advantages[4]


 * Low occurrence of false negatives


 * Extremely low (almost 0%) false positive rates


 * Highly reliable because no two people have the same retinal pattern


 * Speedy results: Identity of the subject is verified very quickly

Disadvantages[4]


 * Measurement accuracy can be affected by diseases such as cataracts and glaucoma


 * Scanning procedure is highly invasive


 * Not very user friendly


 * Limited government, corporate, and other funding


 * Subject being scanned must focus on the scanner from about three inches away


 * High equipment costs


 * Poor lighting can affect results