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Table 1 Correlation between disease severity levels according to the DRSS and ETDRS classification of DR

From: Amine oxidase copper-containing 3 (AOC3) inhibition: a potential novel target for the management of diabetic retinopathy

Disease severity [16] Findings observable upon dilated ophthalmoscopy [16] ETDRS level equivalent [16] Risk assessment [16] Prevalence of vision-related difficulty [17]
No apparent retinopathy No abnormalities Level 10: DR absent   Functional burden: 20.2%
Reading: 11.7%
Noticing objects to the side: 4.4%
Mild NPDR Microaneurysms only Level 20: Very mild NPDR   Functional burden: 20.4%
Reading: 8.5%
Noticing objects to the side: 2.8%
Moderate NPDR More than just microaneurysms but less than severe NPDR Levels 35, 43: Mild, moderate NPDR less than 4:2:1 One-year risk for early PDR:
One-year high-risk PDR: 1.2–3.6%
Level 47: Moderately severe NPDR less than 4:2:1 One-year risk for early PDR:
One-year high-risk PDR: 8.1%
Severe NPDR No signs of PR but with any of the following:
 Extensive (> 20) intraretinal hemorrhages in each of the 4 quadrants
 Definite venous beading in ≥ 2 quadrants
 Prominent IRMA in ≥ 1 quadrant
Levels 53A–53E: Severe to very severe NPDR, 4:2:1 rule One-year risk for early PDR: 50.2% (severe NPDR)
One-year high-risk PDR:
14.6% (severe NPDR)–45.0% (very severe NPDR)
Functional burden: 48.5%
Reading: 33.3%
Noticing objects to the side: 14.5%
PDR  ≥ 1 of the following:
 Vitreous/preretinal hemorrhage
Levels 61, 65, 71, 75, 81, 85: PDR, high-risk PDR, very severe, or advanced PDR  
Ungradable   Level 90: Cannot grade, even sufficiently for level 81 or 85  
  1. DRSS Diabetic Retinopathy Severity Scale, DR diabetic retinopathy, ETDRS Eary Treatment Diabetic Retinopathy Study, IRMA intraretinal microvascular abnormalities, NPDR non-proliferative diabetic retinopathy, PDR proliferative diabetic retinopathy