What is the 4-2-1 Rule? by Dev1 | Sep 6, 2023 | Bookmarking Post, CLINICAL DISTINCTIONS | 0 comments Bookmark Please login to bookmarkClosePlease login Severe NPDR meets one of the criteria defined by the 4-2-1 rule, while Very Severe NPDR meets two of the criteria: 4 quadrants of hemorrhages 2 quadrants of venous beading 1 quadrant of IRMA