Severity of diabetic retinopathy for individual eyes in the study population according to Early Treatment Diabetic Retinopathy Study Scale (Diabetes Control and Complications Trial5)
| Level | Severity | Definition | Right eyes (n) | Left eyes (n) |
| 10 | No retinopathy | Diabetic retinopathy absent | 84 | 84 |
| 20 | Very mild NPDR | Microaneurysms only/1 haemorrhage | 11 | 12 |
| 35 | Mild NPDR | Microaneurysms plus hard exudates, cotton wool spots, and/or mild retinal haemorrhages | 9 | 6 |
| 43 | Moderate NPDR | Microaneurysms plus mild IRMA or moderate retinal haemorrhages | 0 | 2 |
| 47 | Moderate NPDR | More extensive IRMA, severe retinal haemorrhages, or venous beading in one quadrant only | 1 | 0 |
| 53 | Severe NPDR | Severe retinal haemorrhages in four quadrants, or venous beading in at least two quadrants, or moderately severe IRMA in at least one quadrant | 1 | 3 |
| 61 | Mild PDR | NVE < 0.5 disc area in one or more quadrants | 1 | 1 |
| 65 | Moderate PDR | NVE ≥ 0.5 disc area in one or more quadrants or NVD < 0.25–0.33 disc area | 0 | 0 |
| 71–75 | High risk PDR | NVD ≥0.25–0.33 disc area and/or vitreous haemorrhage | 1 | 0 |
| 81–85 | Advanced PDR, fundus partially obscured |
0 |
0 |
↵Diabetes Control and Complications Trial definitions.
NPDR = non-proliferative diabetic retinopathy; IRMA = intraretinal microvascular abnormalities; PDR = proliferative diabetic retinopathy; NVE = new vessels elsewhere; NVD = new vessels on or within 1 disc diameter of optic disc.