No evidence of widespread iris ageing effect, says NIST
15 July 2013 17:40 GMT

No widespread iris degradation says NIST

It is a hotly debated phenomena. Does the human iris age to the point it will affect the day-to-day performance of iris recognition biometric systems? Absolutely not, says a new IREX VI study by the USA's National Institute of Standards and Technology (NIST).

According to the report: "Using two large operational datasets, we find no evidence of a widespread iris ageing effect."

This finding flies in the face of a report by the University of Notre Dame that suggested iris template ageing was a concern.

In the new report, NIST computes 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. The researchers did concede, however, that given the large population sizes, "We identify a small percentage of individuals whose recognition scores do degrade consistent with disease or an ageing effect…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."

There is also a debate over what ageing actually means. The ISO/IEC 19795-1 testing standard defines ageing as any increase in error rates with time. This definition is imprecise, says NIST. This is because temporary changes due to environment (e.g. lighting) or user behavior (e.g. blinking) might yield elevated error rates without any change in the biometric source itself.

NIST's report says that dilation has been suggested to be part of ageing. "Instead we assert that ageing stems from irreversible changes to the anatomy, primarily the iris texture. Dilation should not be considered part of ageing because it varies stochastically and can be mitigated - some iris cameras normalize dilation by shielding or by active illumination."

Corneal shape changes have been suggested as influential on iris recognition too, but their effect has never been quantified.

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