Using red-channel separation gives a better picture in diagnosis of DME.
Screening for diabetes-related eye disease, including diabetic macular edema (DME), involves inspecting retinal photographs. In a new study in Optometry and Vision Science, researchers offer a new technique.
Mastour Alhamami, PhD, of Indiana University School of Optometry, Bloomington and colleagues found that separating out the red color channel can help show some abnormalities more clearly. That is particularly true for racial and ethnic minority patients, the team wrote. That is because these patients have darker pigments in the back of their eyes.
The researchers analyzed standard color fundus photographs from 2,047 adult patients with diabetes. Of these 90% self-identified as members of minority groups. The patients were all in a medically under-served area and lacked access to routine eye care.
Of the group of patients, 148 had significant macular edema, including 13 who had a cystoid pattern of the condition. An important finding was that without separating the red channel, doctors would have missed five of these patients.
"Cysts may be under-detected with the present fundus camera methods, particularly when short-wavelength light is emphasized or in patients with dark fundi," the authors wrote.
That's because the appearance of the macula can change greatly in narrow band illumination.
"Our finding of a clear-cut advantage of red-channel images over the green-channel images was in an underserved population in which the proportion of patients with dark eyes is quite high and the prevalence of retinal complications from diabetes is also expected to be high," they concluded.
The researchers also found that red-channel images may provide more information about damage in the deeper layers of the retina.
"It is not yet known whether cysts in different retinal layers indicate one mechanism that can lead to edema being more important than another, but damage to and early detection in the deeper layers might be enhanced by using longer wavelength techniques," they wrote.
The article is entitled, "Comparison of Cysts in Red and Green Images for Diabetic Macular Edema."