ROP is classified (internationally agreed) by:
- Zone of involvement (centred around the optic disc)
- Stage of appearance
- Presence of ‘plus’ disease – abnormalities of posterior retinal or iris blood vessels
Evidence of ROP in zone 1 (around the optic disc), presence of abnormal vessel formation (stage 3) or ‘plus’ disease carries a poor prognosis without treatment.
Reference: Fleck, B. (2012). ‘Ophthalmology’ in Rennie and Roberton’s ‘Textbook of Neonatology’ 5th Edition. Chapter 33, p839.