Up to 8 million of the roughly 18 million Americans diagnosed with diabetes suffer from vision problems connected with the disease. That connection offers several possibilities for early diagnosis of diabetes.
A team at the University of Michigan Medical School, has developed a device that measures flavoprotein autofluorescence (FA) in the retina. Victor Elner and Howard Petty, professors of ophthalmology and visual sciences, had already shown that a high level of FA is a reliable indicator of metabolic stress and tissue damage in the eye, often caused by impending diabetes. In their latest study, they set out to quantify that finding and check on its possible use for early diagnosis of diabetes. “Our objective was to determine whether we could detect abnormal metabolism in the retinas of patients who might otherwise remain undiagnosed based on clinical examination alone,” says Elner.
To measure levels of FA, the pair devised an instrument that aims 1 ms flashes of light at 467 nm wavelength sequentially at a patient’s two eyes. A charge-coupled-device camera captures the FA response at 535 nm. The system’s software determines the average intensity and the average curve width of the FA by analyzing histograms of pixel intensities for each eye. The noninvasive test takes about five minutes for both eyes.
Elner and Petty used their device to measure the FA levels of 21 individuals diagnosed with diabetes and 21 age-matched healthy controls. They found that FA activity was significantly higher for those individuals with diabetes, however severe their condition. They also compared the FA levels of 12 patients in the group suffering from diabetic retinopathy, a complication of diabetes that can lead to blindness, and patients without any visible eye disease. Patients with diabetic retinopathy in at least one eye, they report in the Archives of Ophthalmology, had notably higher FA activity.
“Increased FA activity is the earliest indicator that cell death has occurred and tissue is beginning to break down,” Petty says. “FA serves as a ‘spectral biomarker’ for metabolism gone awry, and we can use the results to detect and monitor disease.” The system not only has potential for early diagnosis of diabetes, it also has the potential for use in monitoring the progress of the disease. Conventional glucose monitoring based on blood samples does not offer that monitoring ability.
Elner and Petty have filed for patents on their device and have founded a company, OcuSciences, to commercialize the technology. “So much damage occurs before diabetes can be detected by a doctor,” Elner says. “Early diagnosis will allow us to reduce organ damage and prevent many complications that accompany this disease.”
–PG