PROVIDENCE, R.I. -- A new device to measure macular pigment in the human eye will improve research opportunities into the correlation between pigment levels and macular degeneration, the leading cause of blindness in the world for persons over 60, according to its Brown University designer.
The small tabletop device uses light-emitting diodes (LEDs) to measure macular pigment, a yellowish substance in the eye that may protect the eye from the destructive effects of light, according to Bill R. Wooten, professor of psychology, who designed the instrument called the macular densitometer.
Wooten recently found no significant difference between the accuracy of the new device and an existing machine in a study of 30 subjects, ranging in age from 16 to 60. Those results are published in the October issue of Investigative Ophthalmology & Visual Science.
However, unlike traditional machines that rely on complex optical systems to measure macular pigment, the new device is not difficult to assemble or move and can be operated by someone without any expertise, said Wooten.
A patient looks directly into the machine and adjusts a flickering light until it stops flickering, then repeats the process with a flickering light in peripheral vision. By comparing the two measurements, researchers can determine how much light is absorbed by the macular pigment and therefore how much macular pigment a patient has, said Wooten. The whole process takes about 10 minutes.
"We know that macular pigment varies a lot from person to person," said Wooten. "What is unknown is the cause-and-effect relation between the amount of macular pigment and macular degeneration."
Research by Wooten and his colleagues has shown several correlations between levels of macular pigment and macular degeneration in specific situations. These correlations have been documented with factors such as eye color, gender and smoking. Other studies have found associations between dietary intake or blood concentrations of cartenoids (a nutrient found in spinach, kale and egg yolks) and protection from macular degeneration.
There is no known prevention or cure for the disease, which leads to blindness -- a situation Wooten attributes to the fact that there are currently no devices in widespread use for research or clinical use. Because the relationship between measures of dietary intake and retinal concentrations of the pigment is weak, using diet and blood values to predict the density in the eye is not optimal.
"We are taking advantage of the newly available LEDs in this machine," said Wooten. "This system is portable, rugged and accurate and can be used easily in a clinical or research setting."
If the hypothesis about a correlation between macular pigment levels and the disease proves true, ophthalmologists will be interested in measuring the levels in patients without the disease and those with early signs of the disease, said Wooten. The new machine will only be able to measure macular pigment in sighted people. Those in whom the disease has already progressed to blindness will not be able to be measured.
Nine macular densitometers are now in use at the University of Hong Kong Eye Hospital, the University of Pennsylvania Department of Ophthalmology, the University of New Hampshire Department of Nutrition, and the Eye and Ear Infirmary in New York City.
Wooten designed, built and tested the macular densitometer with researchers at the Schepens Eye Research Institute in Boston, Mass., including Billy R. Hammond Jr., Richard I. Land, and D. Max Snodderly. Also providing design input were Robert K. Moore and Ken DeLucia at Brown. Wooten, Snodderly and Land have applied for a patent for the machine.
Journal
Investigative Ophthalmology & Visual Science