A retinal scan or retinal print was a security method by which individuals were identified when accessing critical or secured information. Retinal scans were in use, at least on Earth, since the early 21st century and were still used in the 24th century, although voiceprint access was more common. Retinal scans were taken using a retinal scanner, a device which scanned the retina of a person's eye.
In 2369, Kobliad Security officer Ty Kajada asked Doctor Julian Bashir if he did a retinal imaging scan of Rao Vantika's dead body to confirm that there was no residual activity in his visual cortex. (DS9: "The Passenger")