International Classification of Retinopathy of Prematurity divided retinopathy of prematurity into 3 zones on the retina of the eye so as to facilitate clear communication between ROP experts. There are 3 Concentric Zones, wherein each zone is centered on the optic disc (head of the optic nerve) and normal retinal vessel development proceeds outward from the center of the optic disc toward the extreme periphery of the retina.
- Zone 1 – Circle from centre of disc with radius of twice distance from disc to macula
- Zone 2 – From nasal edge of zone 1 to ora nasally and upto equatot region of retina temporally
- Zone 3 – From temporal crescent of retina anterior to zone II