Some light can be beneficial without interacting with our eyes.
Solid state lighting (SSL) usually conjures up images of lighting fixtures, streetlights, and even flashlights, all designed to help bring day to night so that we can see our way around. But sometimes we need light even though it may never reach our eyes. For example, sunlight helps our bodies produce vitamin D, which is an essential nutrient.
Light also can have therapeutic value under some circumstances. One of the most common uses is for the treatment of newborn babies who have jaundice. Jaundice is a medical condition that occurs when too much of the compound bilirubin builds up in the patient's bloodstream. It can have several causes, but it essentially results from the breakdown of red blood cells. The chemical compound has a bright yellow color, which causes the patient's skin to turn yellow. (The same effect is what causes a bruise to turn yellow as it heals.)
Luma League has developed a DIY design for bili blankets to treat newborns with jaundice in emerging nations around the world, using LEDs and off-the-shelf components.
Low levels of bilirubin are normal, but when levels get too high, they can create a risk of damage to other systems in the body. For this reason, doctors will try to lower the level in babies who show signs of jaundice.
The most effective treatment for this condition is light. As it turns out, the peak absorption wavelength of bilirubin is 458 nm. This light causes the molecules to change into a new form that is more soluble in water, which in turn makes it easier for the body to eliminate it from the blood.
Halogens and their discontents
In the past, physicians have relied on light produced by halogen light sources. They would use a light mounted above the baby, much like a warming lamp, but this required covering the patient's eyes to prevent damage from the bright light. As a result, the "bili blanket" was developed, which uses a light source connected to a diffusing panel, connected by a fiber optic tether. The "blanket" can be applied directly to the baby's skin in the back or on the front, and then the baby can be swaddled and held normally.
The bili blanket eliminates some of the problems of the halogen lamps, such as reducing the exposure to unwanted ultraviolet light. (The ultraviolet emissions could damage the vision of the patient or the caregivers, as well as cause damage to the patient's skin.) The lamps still produce significant amounts of heat and infrared emissions, which can create an unwanted increase in the patient's temperature and lead to hydration problems.
As with other lighting application problems, LEDs offer advantages over traditional solutions. The emissions of the LEDs can be tuned to match the bilirubin absorption frequency more closely. By eliminating the unwanted frequencies, the device is 90 percent more energy-efficient than similar devices using halogen bulbs. And the LED light source is rated for 20,000 or more hours, and reduces the need for maintenance and lamp changes.
LED bili blankets are available from a number of sources, including Natus Medical Inc. and Koninklijke Philips Electronics N.V. There is also an interesting project to make DIY bili blankets available in developing countries using off-the-shelf components to create an array of LEDs. The Luma League has developed designs for low-cost bili blankets and light meters for testing and calibration. The project has been featured at a Maker Faire event, and the developer hopes to make the affordable technology available to hospitals and healthcare providers around the world.