Diabetic Retinopathy Classification and Management

Classification System

The American Academy of Ophthalmology recommends classifying diabetic retinopathy 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, 2
The International Council of Ophthalmology suggests that diabetic retinopathy classification should be based on findings observable on dilated ophthalmoscopy 1, 2

Patients with no apparent retinopathy require screening every 1-2 years, as recommended by the American Diabetes Association 1, 3
The American Academy of Ophthalmology recommends annual follow-up examinations for patients with mild nonproliferative diabetic retinopathy (NPDR) 1, 3
Patients with severe nonproliferative diabetic retinopathy require immediate referral to an ophthalmologist and follow-up every 3 months, according to the International Council of Ophthalmology 1, 3
The American Academy of Ophthalmology suggests that patients with proliferative diabetic retinopathy (PDR) require immediate referral to an experienced ophthalmologist 1, 3

Diabetic macular edema (DME) is assessed independently and can be classified based on location, with categories including no DME, non-center-involving DME, and center-involving DME, as recommended by the American Academy of Ophthalmology 1, 2, 4
The International Council of Ophthalmology suggests that DME can also be graded by proximity to the fovea when OCT is unavailable, with categories including mild, moderate, and severe 1, 5

Any degree of macular edema, severe NPDR, or any PDR requires prompt referral to an ophthalmologist, as emphasized by the International Council of Ophthalmology 1, 3
Systematic screening based on diabetes duration rather than symptoms is essential, as advanced stages of diabetic retinopathy and macular edema can be present even without visual symptoms, according to the American Academy of Ophthalmology 2, 4

The presence of at least one microaneurysm without additional lesions defines mild NPDR according to the International Clinical Diabetic Retinopathy (ICDR) scale (Ophthalmology 2020) 6.

Moderate NPDR is diagnosed when retinal hemorrhages and/or microaneurysms exceed the standard photograph 2A, and may be accompanied by soft exudates, venous beading, or intraretinal microvascular abnormalities (IRMA), provided the findings are less severe than the criteria for severe NPDR (ICDR, Ophthalmology 2020) 6.

Severe NPDR is identified by any one of the following features (ICDR, Ophthalmology 2020):
- Severe intraretinal hemorrhages and microaneurysms equal to or exceeding standard photograph 2A in all four retinal quadrants.
- Venous beading present in two or more quadrants.
- Moderate IRMA equal to or exceeding standard photograph 8A in at least one quadrant.
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High‑risk PDR is defined by either of the following (ICDR, Ophthalmology 2020):
- Neovascularization on or within one disc diameter of the optic disc (NVD) that meets or exceeds standard photograph 10A (≈ ¼–⅓ disc area), with or without vitreous or preretinal hemorrhage.
- Vitreous and/or preretinal hemorrhage accompanied by neovascularization either on the disc smaller than standard photograph 10A, or elsewhere that meets or exceeds one‑quarter disc area.
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Intraretinal microvascular abnormalities (IRMA) are tortuous intraretinal vessels that remain confined within the retinal layers, whereas true neovascular complexes extend into the vitreous cavity; this distinction is essential for correctly classifying severe NPDR versus PDR (ICDR, Ophthalmology 2020) 6.