Misidentified. An eye with iritis.

Tariq Aslam/Moorefields Eye Hospital

Futuristic Scanners Hobbled by Eye Disease

In the futuristic film Minority Report, an eye scanner gives actor Tom Cruise access to the secure police facility where he works. Even in today's world, eye scanners have begun cropping up in airports and at border patrols. Although the technology is billed as much more accurate than fingerprinting, scientists have worried about a potential flaw: If you have an eye infection--or an eye disease--will these scanners still recognize you as you?

Scanners take a picture of the entire eye and then filter out everything but the iris, which is different in each person. They then transform this image into a numerical code, or template. When Tom Cruise goes to work--or you stand in front of a kiosk at the airport--the scanner compares your iris data to what it has on file. As long as about 70% of the template squares up (pupil dilation and lighting prevent perfect matches), the scanner recognizes you. Eye scanners only make a false match in about one in every million cases, which is 10 times more accurate than fingerprints.

But what happens if there's something wrong with your eyes? For example, a conjunctivitis (pink eye) infection can turn the eyes red. So can inflammatory diseases such as scleritis and episcleritis. And an autoimmune condition called iritis causes inflammation that can warp the shape of the iris.

Ophthalmologist Tariq Aslam of Princess Alexandra Eye Pavilion in the United Kingdom and his team gathered 54 patients who had these conditions and took iris scans before and after treatment. "We expected that [the scanners] would fall flat on their faces," says Aslam. Instead, his group found that most of the conditions passed the test. Even glaucoma, whose treatment requires that the iris be punctured with a laser, didn't pose a problem. Only iritis mucked up the scans. Out of the 24 people with the condition, five could not be identified by the scanners after treatment, the team reports online today in the Journal of the Royal Society Interface.

Iritis affects about one in every 1000 people, notes Aslam. Although that may not "sound like a massive amount," he says, "if you consider the amount of people that go through Heathrow Airport [in London, which utilizes the scanners] everyday, it's quite a lot."

Eye-scan engineers have long wondered whether eye problems could interfere with the scanners--and this looks like a good start to figuring that out, says Eliza Du, an electrical engineer who works with iris-recognition technologies at Purdue University, Indianapolis. She says that studying more patients and scanning them before, during, and after the disease would be ideal. Roberto Roizenblatt, an ophthalmologist at the University of California, Irvine, says that the study highlights the fact that it's always important to have a backup identification system in place. No one, he says, should miss a flight because of an eye disease.