In Canada, the current Canadian Pediatric Society recommendations, dating from 2016 are to screen infants for retinopathy of prematurity with Gestational Age <31 weeks or Birth weight <1,251 g.
These recommendations are already somewhat more restrictive than other countries, in the UK the limits are 32 weeks and 1500g, and in the USA <30 weeks or less than 1500 g, plus selected very unstable babies up to 2000g.
The larger and more mature infants are known to be at lower risk than less mature babies. The question that was asked in the study reported in this new publication was whether we really need to screen all those babies. Sabri K, et al. Refining evidence-based retinopathy of prematurity screening guidelines: The SCREENROP study. Paediatrics & child health. 2019.
In this study using data collected by our Canadian Neonatal Network the risks of developing significant RoP and of developing RoP requiring treatment were modelled using multiple different risk factors. There were nearly 5000 screened babies, and they divided RoP into type 1 or type 2 according to ETROP guidelines. Type 1 ROP is defined as
any stage 3 or plus disease in zone 1, or stage 3 and plus disease in zone 2 (and is considered to need urgent treatment). Type 2 ROP is defined as zone 1, stage 1 or 2 without plus disease or zone 2, stage 3 without plus (and is considered to need close follow up to detect progression). Any baby with type 1 or type 2 RoP, or who had detachment without treatment, was considered to be Clinically Significant RoP (CSROP).There were about 460 babies overall with CSROP, and 250 who had intra-ocular treatment with laser or VEGf inhibitors.
The cohort was split into 2/3, used to derive a model, and another 1/3 to validate the model.
In the end only birth weight and gestational age were required to develop a model which identified babies whose risk of CSROP was 1% or more. Using cutoffs of 1200 g birth weight or 30 weeks gestation identified all of the babies with RoP treatment, while screening fewer babies, and including all the babies except one with CSROP, a baby who did not need treatment. If these limits had been applied to this, development, cohort 20% fewer babies would have been screened.
Applying the model to the validation cohort confirmed the findings, and required 30% fewer babies to be screened, without missing any CSROP, except for a baby of over 1800g and over 32 weeks who was screened for specific individual reasons and did not fit the current screening guidelines anyway,
RoP screening is time consuming and the medications and procedure can cause significant instability in the babies. It also hurts (mostly, I think, because of the lid retractors) and analgesic interventions are only partly successful. Sometimes back-transport to level two centers is delayed, or the babies are re-transported back to tertiary centers for their eye exams. Most centers that I know in Canada have a very busy group of pediatric ophthalmologists, with at least intermittent difficulty in assuring timely exams.
For all these reasons, if we can reduce the number of eye exams by eliminating those with very low risk of developing clinically significant RoP, that is surely a good thing.
We have to keep in mind, that on an individual basis there is still the occasional extremely sick baby with prolonged instability who may need to be screened who was larger or more mature than these limits, but the large majority of babies who are over 30 weeks and over 1200 g could be eliminated from screening programs.