What are the stages of diabetic retinopathy classification?

Diabetic Retinopathy Classification

Diabetic retinopathy is classified using the International Clinical Diabetic Retinopathy Disease Severity Scale, which divides the disease into five main stages: no apparent retinopathy, mild nonproliferative diabetic retinopathy (NPDR), moderate NPDR, severe NPDR, and proliferative diabetic retinopathy (PDR), with diabetic macular edema assessed separately. 1

Primary Classification System for Diabetic Retinopathy

The internationally accepted classification system stratifies diabetic retinopathy based on findings observable on dilated ophthalmoscopy 1:

Stage 1: No Apparent Retinopathy

• No abnormalities visible on examination 1
• Patients require screening every 1-2 years 1

Stage 2: Mild Nonproliferative Diabetic Retinopathy (NPDR)

• Microaneurysms only 1
• This represents the earliest clinically detectable stage 1
• Annual follow-up examinations recommended 1

Stage 3: Moderate Nonproliferative Diabetic Retinopathy

• More than just microaneurysms but less than severe NPDR 1
• May include dot and blot hemorrhages, hard exudates, and cotton wool spots 1
• Follow-up every 3-6 months required 1

Stage 4: Severe Nonproliferative Diabetic Retinopathy

• Any of the following findings, but no signs of proliferative retinopathy 1:
  • More than 20 intraretinal hemorrhages in each of four quadrants 1
  • Definite venous beading in two or more quadrants 1
  • Prominent intraretinal microvascular abnormalities (IRMA) in one or more quadrants 1
• This stage requires immediate referral to an ophthalmologist 1
• Follow-up every 3 months 1

Stage 5: Proliferative Diabetic Retinopathy (PDR)

• One or more of the following: neovascularization, vitreous hemorrhage, or preretinal hemorrhage 1
• Represents the most advanced stage with new blood vessel growth 1
• Requires immediate referral to an experienced ophthalmologist 1

Separate Classification for Diabetic Macular Edema

Diabetic macular edema (DME) is assessed independently because it can occur at any stage of retinopathy and follows an independent course 1:

DME Classification Based on Location

• No DME: No retinal thickening or hard exudates in the macula 1
• Non-center-involving DME: Retinal thickening that does not involve the central 1mm subfield zone 1
• Center-involving DME: Retinal thickening involving the central 1mm subfield zone 1

Alternative DME Severity Grading (Clinical Examination)

When OCT is unavailable, DME can be graded by proximity to the fovea 1:

• Mild: Retinal thickening or hard exudates distant from the center of the macula 1
• Moderate: Retinal thickening or hard exudates approaching but not involving the center 1
• Severe: Retinal thickening or hard exudates involving the center of the macula 1

Critical Clinical Implications

Any degree of macular edema, severe NPDR, or any PDR requires prompt referral to an ophthalmologist 1. The International Council of Ophthalmology emphasizes that screening programs should only be implemented when treatment access is available within 3 months 1.

Common Pitfall to Avoid

Do not assume patients are asymptomatic based on their reported vision—advanced stages of diabetic retinopathy and macular edema can be present even without visual symptoms 1. This underscores why systematic screening based on diabetes duration rather than symptoms is essential 2.

The classification system allows prediction of progression risk and guides appropriate referral timing, follow-up intervals, and treatment decisions 1.