Iris and retina scans

The iris has a fine texture that — like fingerprints — is determined randomly whilst the foetus is in the womb, thus making every person's irises unique.
An iris scan works by taking a high resolution image of the iris, converting the pattern into a mathematical representation and comparing this to a template of digital images.
Because the process is similar to taking a photo, it is fairly unobtrusive and can be performed up to a few metres away from the individual. However, as with facial recognition technology, there is still the problem of 'live tissue verification', which means that the system needs to be supervised.
The United Arab Emirates has used iris recognition at all its border controls since 2001.