Classification of Diabetic Retinopathy
Diabetic retinopathy is primarily classified into two main categories: Non-Proliferative Diabetic Retinopathy (NPDR) and Proliferative Diabetic Retinopathy (PDR), with Diabetic Macular Edema (DME) as a separate classification that can occur at any stage. 1
Main Classification Categories
1. Non-Proliferative Diabetic Retinopathy (NPDR)
NPDR represents the early stages of diabetic retinopathy characterized by vascular abnormalities without neovascularization. It is further subdivided into:
- Mild NPDR: Characterized by microaneurysms only 1
- Moderate NPDR: More than just microaneurysms but less than severe NPDR 1
- Severe NPDR: Any of the following (without signs of proliferative retinopathy) 1:
- More than 20 intraretinal hemorrhages in each of four quadrants
- Definite venous beading in two or more quadrants
- Prominent intraretinal microvascular abnormalities (IRMA) in one or more quadrants
2. Proliferative Diabetic Retinopathy (PDR)
PDR is the advanced stage representing an angiogenic response of the retina to extensive ischemia from capillary closure. It is characterized by 1:
- Neovascularization (new vessels on the disc or elsewhere)
- Vitreous/preretinal hemorrhage
PDR can be further classified as high-risk when it includes 1:
- New vessels on or near the optic disc (NVD) occupying ≥1/4 to 1/3 disc area
- Any neovascularization with vitreous hemorrhage
3. Diabetic Macular Edema (DME)
DME is assessed separately from the stages of DR as it can occur at any stage of retinopathy. It is classified as 1:
- DME apparently absent: No apparent retinal thickening or hard exudates in posterior pole
- DME apparently present: Some apparent retinal thickening or hard exudates in posterior pole
- Mild: Retinal thickening or hard exudates distant from the center of the macula
- Moderate: Retinal thickening or hard exudates approaching the center of the macula but not involving it
- Severe: Retinal thickening or hard exudates involving the center of the macula
With OCT imaging available, DME can also be classified as 1:
- Non-center-involving DME: Retinal thickening in the macula that does not involve the central subfield zone (1 mm in diameter)
- Center-involving DME: Retinal thickening in the macula that involves the central subfield zone (1 mm in diameter)
Clinical Features and Pathophysiology
Classic Retinal Lesions
The classification is based on the presence of specific retinal lesions 1:
- Microaneurysms
- Intraretinal hemorrhages
- Venous beading (alternating areas of venous dilation and constriction)
- Intraretinal microvascular abnormalities (IRMA)
- Hard exudates (lipid deposits)
- Retinal neovascularization
Progression Risk
The classification has clinical significance because the risk of progression and visual loss increases with severity level 1. Correct identification of DR severity allows for:
- Prediction of progression risk
- Determination of appropriate referral timing
- Establishment of follow-up intervals
- Treatment recommendations
Important Clinical Considerations
- Advanced stages of DR and DME may be present even in asymptomatic patients 1
- Patients with moderate or severe NPDR should be referred to an ophthalmologist 1
- Patients with severe NPDR are candidates for panretinal photocoagulation 1
- Patients with high-risk PDR or neovascular glaucoma should receive prompt panretinal photocoagulation 1
- Patients with center-involving DME should be considered for prompt treatment 1
Follow-up Recommendations
Based on DR classification, follow-up intervals should be 1:
- No retinopathy: Every 1-2 years
- Mild NPDR: Annually
- Moderate NPDR: Every 3-6 months
- Severe NPDR: Every 3 months
- During pregnancy: Before pregnancy or in first trimester, then every 3 months until 1 year postpartum
This classification system provides a standardized approach to evaluating diabetic retinopathy severity, guiding clinical decision-making, and improving patient outcomes by enabling timely intervention to prevent vision loss.