Gut and eyes
Retinopathy of prematurity: who to screen, and classification
Checks a baby against the UK and US ROP screening criteria, with the international classification (zones, stages, plus disease) for reading eye reports.
For education. Check against your unit's guidance and a second clinician before use.
weeks
days
Enter the gestation, the birth weight, or both.
International Classification of ROP, third edition (ICROP3), in brief
| Term | Meaning |
|---|---|
| Zone I | Innermost circle around the optic disc (radius twice the disc-to-fovea distance) |
| Posterior zone II | A band two disc diameters beyond zone I |
| Zone II | From zone I to the nasal edge of the retina (ora serrata) |
| Zone III | The remaining outer crescent on the temporal side |
| Stage 1 | Demarcation line between vascular and avascular retina |
| Stage 2 | Ridge |
| Stage 3 | Extraretinal new vessels growing from the ridge |
| Stage 4 | Partial retinal detachment (4A sparing the fovea, 4B involving it) |
| Stage 5 | Total retinal detachment (5A, 5B, 5C) |
| Plus disease | Dilated, tortuous vessels at the back of the eye (pre-plus: less than plus) |
| A-ROP | Aggressive ROP: fast-progressing disease, often in the most preterm babies |
How this is calculated
- Screen if gestation at birth is under 31+0 weeks OR birth weight is under 1501 g (UK RCPCH guideline; the core AAP 2018 criteria are effectively the same). The table summarises the international classification (ICROP3) used in eye examination reports.
Sources
- RCPCH. UK screening of retinopathy of prematurity: clinical guideline.
- Fierson WM; American Academy of Pediatrics Section on Ophthalmology, et al. Screening examination of premature infants for retinopathy of prematurity. Pediatrics 2018;142:e20183061.
- Chiang MF, et al. International Classification of Retinopathy of Prematurity, Third Edition. Ophthalmology 2021;128:e51-e68.
Checked by NICUlearn, 6 Oct 2026.