olemus
silmapõhi, silmamuna seinakihi seesmisim kiht;
reetina soontevõrgu muster on füüsiline biomeetrik

Wiktionary:
(ophthalmology) the thin layer of cells at the back of the eyeball that contains rods and cones sensitive to light, which trigger nerve impulses that pass via the optic nerve to the brain, where a visual image is formed

piltlikult
https://duckduckgo.com/?q=retina&t=h_&iax=images&ia=images

ülevaateid
https://en.wikipedia.org/wiki/Retina

https://en.wikipedia.org/wiki/Retinal_scan

https://www.axonwireless.com/biometric-iris-and-retina-scanner-device/

https://biometrictoday.com/differences-between-iris-recognition-and-retina-scanning/