The treatment of retinopathy of prematurity (ROP) continues to evolve, and it is good to see that earlier treatment at high-risk prethreshold ROP, compared with conventional management with treatment at threshold, improves the structural outcome, and that this is maintained at 2 years after intervention.¹ It is also encouraging to note that there was no increase in adverse ocular outcomes by this earlier treatment. Owing to reclassification of some eyes which underwent vitreoretinal surgery, there was an increase in unfavourable structural outcome between 6 and 9 months, but thereafter they were similar in indicating an encouraging degree of ocular stability.

So far so good, but the revised indications for the treatment of ROP emanating from the Early Treatment of ROP (ETROP) randomised trial² require a major change in clinical practice that must be incorporated into clinical guidelines. Unsurprisingly, these recommendations have generated considerable published^3–7 and unpublished debate. This broadly centres on issues relating to the breaking down of the main ETROP cohort into subgroups based on zone, stage and the presence of plus disease. Concerns have been expressed that following the ETROP recommendations will result in unnecessary treatment of eyes that fall into one or more of the categories that might resolve spontaneously, notably zone II, stage 2+. This is not a trivial issue, as the outcome of these discussions will necessarily feed into clinical guidelines for ROP screening and treatment.

To get to the heart of the matter, we need to consider the concept of “threshold” ROP that was fundamental to the design of the CRYO-ROP study⁸ and is now firmly embedded in …