Threshold disease is considered to be present when stage 3 ROP is present in either zone I or zone II, with at least 5 continuous or 8 total clock hours of disease, and the presence of plus disease.
Granična bolest se smatra prisutnom kad je stadij 3 prematurne retinopatije vidljiv bilo u zoni I ili zoni II, sa najmanje 5 kontinuiranih ili 8 ukupnih sati bolesti, te uz prisutnost «plus» bolesti.