Retinal scan

[3] A retinal scan is performed by casting an unperceived beam of low-energy infrared light into a person’s eye as they look through the scanner's eyepiece.

[4] The idea for retinal identification was first conceived by Carleton Simon and Isadore Goldstein and was published in the New York State Journal of Medicine in 1935.

In 1976, Robert "Buzz" Hill formed a corporation named EyeDentify, Inc., and made a full-time effort to research and develop such a device.

[7] Because of the relative obscurity and "high tech" nature of retinal scans, they are frequently used as a device in fiction to suggest that an area has been particularly strongly secured against intrusion.

Likewise, indications of chronic health conditions such as congestive heart failure, atherosclerosis, and cholesterol issues first appear in the eyes.