Frequency distribution of infants according to type of retinopathy of prematurity (ROP) at different gestational age (GA) and birth weight (BW) (N=851)
| GA | Severe ROP | Type 1 ROP | Type 2 ROP | ROP not prethreshold | Subtotals | No ROP | Total |
| GA | |||||||
| <29 | 9 | 5 | 2 | 21 | 37 | 50 | 87 |
| 29–30 | 4 | 7 | 4 | 20 | 35 | 122 | 157 |
| 31–32 | 8 | 8 | 3 | 15 | 34 | 251 | 285 |
| 33–34 | 2 | 1 | 0 | 6 | 8 | 224 | 233 |
| 35–36 | 0 | 0 | 0 | 2 | 2 | 70 | 72 |
| >36 | 0 | 0 | 0 | 1 | 1 | 16 | 17 |
| Total | 23 | 21 | 9 | 65 | 118 | 733 | 851 |
| BW | |||||||
| <1000 | 5 | 6 | 2 | 14 | 145 | 36 | 63 |
| 1000–1599 | 15 | 13 | 6 | 41 | 75 | 387 | 462 |
| 1600–1999 | 2 | 1 | 1 | 7 | 11 | 188 | 199 |
| ≥2000 | 1 | 1 | 0 | 3 | 5 | 122 | 127 |
| Total | 23 | 21 | 9 | 65 | 118 | 733 | 851 |