Classification of ROP :

4. Threshold ROP:
During older times this stage of ROP (Fig 4) signified the need to treat the child with the LASER or CRYO therapy. However, presently the treatment is indicated at Prethreshold stage.23

Figure 4: Threshold ROP :

5. Prethreshold ROP:
ETROP: Early treatment of Retinopathy of Prematurity, A randomized controlled trial, convincingly demonstrated that treatment before the Threshold stage; the stage at which treatment was recommended previously, can reduce the incidence of unfavorable structural outcomes from 15.6% to 9.0%. Hence, currently most eye surgeons prefer to treat the premature babies with ROP at Prethreshold stage.

Presence of the plus disease with presence of neo-vascularization in zone 1 or 2 is an easy definition of pre-threshold ROP