ROP’s progress is noted by zones and stages. The zone means where it’s occurring. The stage means how bad it is.
Zone 1 is the centermost point of the eye.
Zone 2 is around the center.
Zone 3 is around the outer edge of the retina.
Zone 1 is the most serious, and zone 3 the least.
There are 5 stages of ROP. Stage 1 has the least damage. Stage 5 is when the retina is detaching. Most of the time, doctors won’t recommend treatment until it gets to stage 3.