Invisible Color Variations of Facial Erythema: A Novel Early Marker for Diabetic Complications?

Figure 2

Histograms showing the frequency distributions of the invisible facial redness (IFR) at the two cheeks of one diabetic patient (the least reddish cheek, , and the most reddish cheek, ) and the two cheeks of one nondiabetic subject (the least reddish cheek, , and the most reddish cheek, ). In each distribution, the standard deviation, , measures how spread out the data is, whereas the arithmetic mean () measures where the data is centered.