The iris of human eye is located behind the cornea and in front of the lens. It consists of many collagen fibers, shriveled veins, crowns, chyme, pigments, serpentine microtubules, stripes, freckles, cracks and pits, and its color changes with the quantity and distribution of pigments. Through the cornea, we can see that the iris is disc-shaped, and there is a small hole in the center called pupil, which can automatically shrink or expand according to the light and shade of the environment.
Iris is unique because the composition of this organ itself is very complicated. The intricate structure of iris surface is because its structural composition depends on embryonic genes. In addition, iris also has the limitations of gene phenotype (not only the morphology, function, appearance of pigment and general appearance texture). Even identical twins have different iris characteristics. Therefore, whether the genomes are the same or not, each iris in each pair has a single particularity, which is no different from the uniqueness of each fingerprint. Therefore, it is very unlikely that the two irises are statistically identical.
Some people think that retina has more unique biological characteristics than iris. Retina is an extremely fixed biological feature, which will not age, wear and tear, and will not be affected by diseases. Retinal recognition technology is to directly irradiate the back of eyeball with laser to obtain the characteristics of retina. Users don't need to touch the device directly, because the retina is invisible, so it won't be forged.