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• Microneurysms: These are first clinically detectable lesions in the fundus. They appear as small, round, red dots temporal to the macula they arise from weekend capillary walls after loss of pericytes.
• Retinal haemorrhages: They are of two types:
  • Dot and blot haemorrhages are found in the deeper layers. Dot haemorrhages are clinically indistinguishable from the microneurysms and blot haemorrhages have fuzzy borders.
  • Flame shape haemorrhages are found in the superficial nerve fiber layer.The source of these haemorrhages are fragile capillaries and thin- walled microaneurysms.
• Hard exudates are lipoprotein deposits with a yellow waxy appearance and distinct margins. They are seen in clumps or in rings. When seen in a rings it is referred to ascircinate retinopathy and usually has a leaking microaneurysm in its centre.
• Soft exudates or cotton wool spots are infarcts of nerve fiber layer caused by arteriolar closure. They are swollen retinal axons seen as zone of retinal swelling that appears as a fluffy white opacification of the inner retinal layers.
• Venous changes that signify retinal ischaemia are venous beading, dilatation, sausage-like segmentation, reduplication of a venous segment and abnormal loop formation.
• Arteriolar changes that are seen are narrowing and obliteration resulting in white thread like arterioles.
• Intra-retinal microvascular abnormalities (IRMA) are shunt vessels which resemble focal areas of new vessels. They are intraretinal in location and do not cross major blood vessels and leak minimally on fluorescein anigiography.
• Neovascularisation on the disc (NVD) are new vessels on or within one disc diameter of the optic disc.
• Neovascularisation elsewhere (NVE) are new vessels any where in the retina and greater than one disc diameter from the optic disc margin.

• Mild NPDR: At least one microaneurysms and or more of the following: Retinal heamorrhage, hard exudates or soft exudates.
• Moderate NPDR:Haemorrhages or microaneurysms or both (approximately 20 dot and blot haemorrhages) in one quadrant as well one or more of following: Soft exudates, venous beading or IRMA. The mild to moderate NPDR was earlier referred to as Background Diabetic Retinopathy (BDR).

Moderate non-proliferative diabetic retionopathy.

• Severe NPDR:This is detected by evaluating the mid peripheral quadrants using the 4-2-1 rule10. Patients with any of the following features are considered to have severe NPDR:
  • Severe intraretinal haemorrhages and microaneurysms in all 4 quardrants.
  • Venous beading in 2 or more quadrants.
  • Moderate IRMA in at least 1 quadrant.
• Very severe NPDR is when at least any 2 of the above features are present.
  

• Early PDR or non-high risk PDR :Characterised by NVD or NVE. Definition not met for high-risk PDR.
• High risk PDR :NVD > 1/3 – ½ disc area.
  NVD with vitreous or preretinal haemarrhage.
  NVE > ½ disc area with preretinal or vitreous haemorrhage.

Proliferative diabetic retinopathy.
NVD:Neovascularisation on Disc. NVE: Neovascularisation elsewhere

• Thickening of the retina located within 500 µ from the center of the macula.
• Hard exudates with thickening of the adjacent retina located within 500 µ from the center of the macula.
• A zone of retinal thickening, 1 disc area or larger in size located within 1 disc diameter from the center of the macula.

• Macular oedema.
• Macular ischaemia.
• PDR with tractional retinal detachment involving the macula.
• Vitreous haemorrhage and subhyaloid haemorrhage.
• Neovascular glaucoma.