Participants' characteristics
| Variable | Normal group (n=18) | Diabetes group (n=23) | NPDR group (n=35) | p Value* |
| Age, years (range) | 41.5 (21–59) | 43.5 (19–58) | 47.3 (27–61) | 0.23 |
| Gender, % men | 28% | 39% | 49% | 0.331 |
| Race, % white | 87% | 91% | 94% | 0.536 |
| DM type, % Type 1 | NA | 48% | 49% | 0.956 |
| DM duration, years (range) | NA | 13 (2–35) | 20 (7–38) | 0.0003 |
| HbA1c, % (range) | 5.2 (4.6–6.1) | 7.1 (5.6–9.7) | 8.7 (6.4–16.3) | <0.0001 |
| ETDRS severity | ||||
| No diabetic retinopathy | 18 | 23 | 0 | |
| Microaneurysms only | 0 | 0 | 9 | |
| Mild NPDR | 0 | 0 | 13 | |
| Moderate NPDR | 0 | 0 | 9 | |
| Moderately severe NPDR | 0 | 0 | 2 | |
| Severe NPDR | 0 | 0 | 2 | |
↵* For comparison among groups, χ2 tests were used for categorical variables and Kruskal-Wallis tests for continuous variables.
DM, diabetes mellitus; ETDRS, Early Treatment of Diabetic Retinopathy Study; HbA1c, glycosylated haemoglobin; NA, not applicable; NPDR, non-proliferative diabetic retinopathy.