The Threshold of the Severity of Diabetic Retinopathy below Which Intensive Glycemic Control Is Beneficial in Diabetic Patients: Estimation Using Data from Large Randomized Clinical Trials

Table 2

The Diabetic Retinopathy Disease Severity and International Clinical Diabetic Retinopathy Disease Severity Scales.

Disease severity level	Findings observable upon dilated ophthalmoscopy
No apparent retinopathy	No abnormalities
Mild NPDR	Microaneurysms only
Moderate NPDR	More than just microaneurysms but less than severe NPDR
Severe NPDR
U.S. definition	Any of the following (4-2-1 rule) and no signs of proliferative retinopathy: (i) Severe intraretinal hemorrhages and microaneurysms in each of four quadrants; (ii) Definite venous beading in two or more quadrants; (iii) Prominent IRMA in one or more quadrants
International definition	Any of the following and no signs of proliferative retinopathy: (i) More than 20 intraretinal hemorrhages in each of four quadrants; (ii) Definite venous beading in two or more quadrants; (iii) Prominent IRMA in one or more quadrants
PDR	One or both of the following: (i) Neovascularization; (ii) Vitreous/preretinal hemorrhage

IRMA = intraretinal microvascular abnormalities; NPDR = nonproliferative diabetic retinopathy; PDR = proliferative diabetic retinopathy. Note: any patient with two or more of the characteristics of severe NPDR is considered to have very severe NPDR. PDR may be classified as high risk or not high risk.