blue background pattern resembling fiber-optic wires

Envisioning a Better Test

By Jim Schnabel

In a medical journal shortly after the Civil War, a North Carolina doctor named Robert Hicks described a mysterious but nearly epidemic affliction he had seen among Confederate troops: “The soldier, who had marched all day without inconvenience, would complain of blindness upon the approach of early twilight, and make immediate application for transportation in an ambulance.” Hicks found that if he held a candle near an affected soldier’s eyes after sundown, “the pupils refuse to respond; and such was the uniform result in all my investigations.”

Hicks suspected that a poor diet caused the condition, and he was right. “Night blindness is now recognized as a classic sign of a lack of vitamin A,” says Alain Labrique, PhD ’07, MHS ’99, MS, an assistant professor in International Health.

With the help of a TV repairman in rural Bangladesh, and more recently a team of spacecraft imaging engineers, Labrique has turned Hicks’ long-forgotten candle-in-the- dark method into an automated, noninvasive device for assessing vitamin A deficiency, still a major cause of illness and early death in low-income countries.

“It’s shaping up to be a major advance in the field of micronutrient assessment,” says Keith P. West, DrPH ’87, MPH ’79, RD, the George G. Graham Professor of Infant and Child Nutrition at the Bloomberg School.

The traditional method for assessing vitamin A levels is the taking of a blood sample, which can be problematic in a low-income setting, because of the logistics involved in sophisticated blood tests as well as local taboos or fears about drawing blood. “There’s a definite need for easier and less invasive methods for assessing vitamin A levels in the field,” says Labrique.

In the 1980s, micronutrient research pioneer Alfred Sommer, MD, MHS ’73, Dean Emeritus of the Bloomberg School, unearthed Robert Hicks’ 1867 journal article, and he and others soon developed field techniques for measuring pupillary responses to weak light stimuli. These techniques worked in principle but were never adopted widely, among other reasons because they required dark, often hot, rooms or tents, and could be difficult to apply in people whose pupils were hard to distinguish from their dark irises.

While serving as an onsite scientist for a major vitamin A assessment and supplementation project in rural Bangladesh earlier this decade, Labrique had an inspiration. The project had just purchased a video recorder, and Labrique noticed that when he aimed it at a person’s face with the infrared night-vision feature switched on, normally dark irises appeared light-colored. Thus he could see people’s dark pupils very clearly.

Using a pair of swim goggles, a compact wireless video camera, a tiny light bulb, and lots of black tape and spray paint, Labrique fabricated a quick prototype in his basement, and refined it with the help of a village TV repairman. In basic tests this “portable field dark adaptometer” performed well enough to earn grants for further development, ultimately by engineers at Johns Hopkins’ Instrument Development Group, who had been working on the James Webb Space Telescope and other NASA programs. They turned it into a simple, robust system that can be plugged into a laptop’s USB port, and digitally record the pupil responses to a series of light stimuli—without the need for a dark room. “I just got back from Kenya, where in less than three hours, I trained five people to use this device,” says Labrique.

Labrique hopes that current testing of prototypes among Kenyan schoolchildren and pregnant Bangladeshi mothers will lead to further tweaks by engineers and widespread field use of the screening tool starting in 2011 or so. And since cardiovascular disease and diabetes also can affect the pupillary response, he notes that in principle the device could someday be used to screen inexpensively for these conditions.

“It’s been getting rave reviews at conferences,” says West. “And other investigators have been approaching us, saying, ‘Hey, can we have one of those to work with?’”