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IREX VI - Temporal Stability of Iris Recognition Accuracy (United States National Institute of Standards and Technology - NIST)
Using two large operational datasets, we find no evidence of a widespread iris ageing effect. Specifically, the population statistics (mean and variance) are constant over periods of up to nine years. This is consistent with the ability to enroll most individuals and see no degradation in overall recognition accuracy. Furthermore, we compute an ageing rate for how quickly recognition degrades with changes in the iris anatomy; this estimate suggests that iris recognition of average individuals will remain viable over decades.There's a whole lot o tehcnical detail on the full report.
The executive summary continues on to say...
However, given the large population sizes, we identify a small percentage of individuals whose recognition scores do degrade consistent with disease or an ageing effect. These results are confined to adult populations. Additionally, we show that the template ageing reported in the Notre Dame studies is largely due to systematic dilation change over the collection period. Pupil dilation varies under environmental and several biological influences, with variations occuring on timescales ranging from below one second up to several decades. Our data suggests that the natural constriction of pupil size over decades does not necessitate re-enrollment of a well enrolled iris.
