*4.3.2. Retina*

Retinal scanning of the eye is a relatively problematic process that cannot be easily imitated. To cheat such a sensor, it would be necessary to use a spoofed eye with the same characteristics as a live eye, which is a very complicated and nearly impossible to replicate (the use of medical ophthalmologic eye phantoms should be taken into account). There is not much information about the liveness test on the retina, but it could again take advantage of medical information, for example, that the non-living retina has a different color. Light refraction of the retina or blood flow in blood vessels may also be tested.

Since the eye is a very sensitive organ, an invasive method cannot be used for this reason. There is a similar liveness test as for the iris; however, this testing can be used to cheat the system when the right eye is replaced by a false (spoofed) eye after a successful test life. For this reason, it is more appropriate to test liveness with another method. The first test is to test the color of the yellow spot. It is done during the use of the scanned eye. It is only with the dead person that the yellow spot becomes yellow, until then it is reddish.

Another option is to test liveness using eye movements. The same principle is used in medicine when examining the eye background. The medical doctor needs to see the whole retina and not just the part seen from a direct view. Therefore, the device is equipped with a deliberate point that the patient watches to slightly retract the eye, allowing the doctor to monitor almost the entire retina. This principle can also be used to test for liveness. The device is equipped with a similar observation point and moves it several times. In each relocation, it performs scans of the retina and compares the position of the blind or the yellow spot. If it is in another place after each scan, it is a living eye.
