Understanding monitoring for ROP

Although blindness from ROP is almost entirely avoidable preterm infants can still become blind, even in settings where services to detect and manage ROP are in place. The effectiveness of any intervention is measured by how well it improves the health of the population. This is often influenced by many factors.

To assess how effective an ROP service is in preventing blindness amongst preterm babies we need to consider these key factors:

• Coverage: % of units with ROP services
• Access to screening: % of babies who should be screened who are screened
• Quality of screening: % of babies who receive the correct diagnosis, and
• Adherence to all screening: % of parents who adhere to screening appointments after discharge.
• Access to treatment: % of babies with sight threatening (Type 1) ROP who are treated
• Quality of treatment: % with good outcomes.

In an ideal setting, all these factors would be functioning at 100%. This means that all eligible babies are screened well and on time, and all needing treatment receive excellent care. The net result would mean there is no ROP blindness in the population.

However even if one of these factors is sub-optimal, blindness can occur. Imagine a scenario where an ROP service has been put in place but is only provided in half of the neonatal units in a region or country, so coverage is only 50%. In addition, only 75% of the eligible babies are actually being screened in these units.

To estimate the effectiveness of this ROP service at the population level we multiply all the variables together. So, in this scenario the effectiveness is: Coverage (50%) x Access to screening (75%) x Quality of screening (100%) x Adherence to follow up (100%) x Access to treatment (100%) x Quality of treatment 100% = 37.5%.

In this population, the ROP services will prevent less than half (37.5%) of all ROP blindness.

Professor Clare Gilbert (global ROP expert and lead educator on this course) says: ‘I often talk to ophthalmologists who are screening, and ask them ‘What proportion of babies who should be screened in this unit do you think you are screening?’ Some look at me a bit oddly, and say ‘All of them, of course.’ This situation is far more likely if the neonatal team are not actively engaged in the screening process, and lists of eligible babies who should be screened every week are not provided. Under these circumstances the ophthalmologists will only screen the eligible babies who are present on the day and they think they are screening all who should be screened. What they do not appreciate is that eligible babies may have been discharged the day before, or they do not know whether babies are returning in the right numbers to be screened after discharge – they just screen those who attend.’