Retinopathy of Prematurity

With inputs from Prof Clare Gilbert, ICEH
Retinopathy of prematurity (ROP) is a potentially avoidable cause of irreversible, and usually total blindness in infants who are born premature. It is a major cause of blindness in children in middle-income countries and south-east Asia and has lifelong implications for the child and their family.
ROP was a major cause of blindness in the USA and Western Europe 50-60 years ago. This occurred because all preterm infants were given 100% oxygen whether they needed it or not. Oxygen is highly toxic to blood vessels, including those in the retina. After the role of oxygen was understood, and it was used less freely, blindness from ROP declined dramatically. Until very recently ROP was, therefore, seen as a condition of the west, and an iaterogenic problem that had been solved. ROP was not included in text books for nurses or paediatricians.
Over the last 10-15 years it has become clear that ROP is rearing its head again and is a major cause of blindness in children in middle-income countries in Latin America, Eastern Europe and the emerging economies of SE Asia (e.g. Vietnam). It is being increasingly reported in China and India. This is happening because these countries are expanding neonatal care, but do/did not know about ROP.
Control entails improving neonatal care, the delivery of oxygen in particular, and detecting infants who develop the treatable stages of disease, followed by laser to the peripheral retina. Both these aspects of control are effective at reducing blindness from ROP.

Blindness from ROP can be controlled through 2 broad approaches:

  • reducing the incidence through excellent neonatal care
  • detecting and treating infants who develop the severe stages of disease

Population at risk:

  • WHO estimate that there are 15 million preterm births a year (born at <37 weeks)
  • Infants born preterm contribute disproportionately to under 5 mortality rates (40% overall)
  • Ministries of Health are highly likely to expand neonatal intensive care as a consequence: this will lead to increased survival of preterm babies, so putting them at risk of ROP
  • UNICEF is supporting the development of neonatal intensive care units in India
  • Those most at risk of ROP are those born at <32 weeks gestational age; babies 32-37 weeks are at less risk.
  • India has the largest number of preterm births of any country (ref WHO Born Too Soon, 2012)
  • Only preterm babies cared for in neonatal intensive care units develop ROP
  • Factors which increase the risk of ROP include preterm birth; too much oxygen; sepsis; chronic lung disease; poor nutrition i.e. less than perfect neonatal care

Preterm births by gestation age and region for 2010  Estimated numbers of preterm births in 2010

ROP the disease:

  • Well established classification system
  • Natural history is known: signs develop 3-4 weeks after birth; progression is rapid, but in around 70% of infants the condition resolves without treatment (i.e. 5-10% of all babies screened). It is those who progress who need treatment
  • Clinical trials show that treatment of the disease once it reaches a critical stage is highly effective at preventing progression to blinding retinal detachment

Strategies for control:

  1. Prevent preterm birth: a challenge as multifactorial
  2. Improve neonatal care: again, a challenge, but specific interventions such as reducing infection and using less oxygen, and using it more carefully, can reduce the risk. Better oxygen monitoring requires
    • systems for delivering oxygen in varying amounts (blenders)
    • systems for measuring oxygen levels in the blood (probes and monitors)
    • trained staff who understand the importance of controlling oxygen levels
  3. Detect infants with disease needing treatment. This can be done in the following ways:
    • Neonatologist identifies infants to be examined according to gestation age, birth weight etc criteria
    • Ophthalmologist visits the neonatal unit on a fixed day and time each week to examine the infants using an indirect ophthalmoscope. For each infant they have to decide a) safe to discharge, or b) see again next week, or c) treatment needed
    • As above, but instead of using an indirect ophthalmoscope, a RetCam (wide field digital camera) is used. Advantages: can take images to track change over time; useful for educating staff and counselling parents. These cameras are portable and can be used in more than one unit
    • Instead of the ophthalmologist using the RetCam a trained technician captures the images. There are then two options:
      • The technician is trained to interpret the images themselves and decide a) safe to discharge, or b) see again next week, or c) needs to be seen by an ophthalmologist, or
      • Images are uploaded onto the internet for remote reading by experts. Challenge: report MUST be fed back to the screener within 48 hours in case treatment is needed – this requires 24/7 access to remote experts
Challenge: infants can develop the stages needing treatment after they have been discharged. They need to be examined too. Any system of detection HAS to be able to respond to this situation as well.
  1. Treatment
    • Indications – infants who develop the constellation of clinical signs known as Type 1 ROP.
    • Methods: laser retinal photocoagulation, under sedation or general anaesthesia. The same laser can be used for other retinal conditions e.g. diabetic retinopathy
    • Timing – treatment MUST be given within 48 hours as it can progress very rapidly to untreatable retinal detachment.
    • Follow up: weekly to make sure getting better. Can retreat.
  1. Long term follow up: 

Infants with ROP have a massively increased risk of other pathology: high degrees of myopia; squint; cortical brain damage. They need regular follow up so these problems can be detected and managed.