The ET-ROP group classified the ROP by those who need treatment immediately or those who doesn't need treatment, The classification is the following Type 1 ROP-->ROP zone I any stage with plus, zone I stage 3 without plus, zone II stage 2 y 3 with plus Type 2 ROP --> Zone 1, Stage 2 or 3 without plus, and Zone II, stage 3 without plus.