Dr Arameh Aghababaie, Dr Hesham El Sayed
So, it’s your first day in the neonatal unit, and you keep hearing the term “ROP” being bandied around. Retinopathy of prematurity – hang on, premature babies can also have eye problems? Don’t they have enough issues as it is?!
We will go through what ROP is, who needs screening, when we screen, what we mean by stages and zones when diagnosing, and how to treat it. And I’ll try to avoid making any cornea eye puns.
What is ROP?
Very preterm or very low birthweight infants have incomplete vasculogenesis at the retina at the time of birth, and once they are born they can undergo abnormal proliferation of the developing retinal blood vessels. These abnormal blood vessels spread throughout the retina. Unfortunately these vessels are fragile and are prone to leaking, which can scar the retina.
When these scars shrink, it can cause the retina to detach, leading to visual loss and sometimes blindness in this group of babies. This is known as Retinopathy of Prematurity (ROP). ROP can lead to myopia, strabismus, amblyopia, and glaucoma.
Usually there are no symptoms in the neonatal period – that’s why screening is in place. Late clinical signs may be unusual eye movements or white pupils.
What causes ROP?
The cause of this abnormal angiogenesis has been theorised but not concretely proven. If we take a look at the eye’s embryology (remember that awful lecture in medical school?), the eye starts to develop at 16 weeks of pregnancy, where the retinal vessels begin to form at the optic nerve and gradually grow towards the edges of the developing retina. In the final trimester, the eye develops rapidly and by full-term, retinal vessel growth is usually complete. However, in very preterm babies, these blood vessels fail to reach the edges of the retina and vessel growth is halted, causing ischaemia to the peripheral retina. It is believed this promotes the release of signalling proteins to promote angiogenesis, which leads to this abnormal angiogenesis.
The majority of babies screened for ROP have a mild case and do not require any treatment. However, some babies may have moderate or severe ROP, and can lead to lifelong visual impairment or blindness if left untreated. In the UK, 4% of babies screened had severe ROP.
Which babies are at risk?
Babies who are born at <32 weeks or are <1.5kg are more at risk of ROP and are therefore screened, however you’re more likely to be affected by ROP the more preterm or small you are!
ROP screening is done at 4 weeks of life for babies meeting the following criteria at birth:
- <32 weeks
To most people’s surprise when you’re learning about neonates, high oxygen delivery to the preterm infant can actually increase the risk of ROP! This was noticed back in the day when very preterm babies were kept in those hyperbaric oxygen chambers after delivery and as a result, ROP levels skyrocketed. This is because the high levels of oxygen promote the abnormal angiogenesis described above. Therefore it’s important to titrate your oxygen levels to deliver the amount required to maintain a preterm’s sats just above 90%!
Other factors that may enhance your risk of ROP is anaemia, requiring blood transfusions, and respiratory distress, requiring mechanical ventilation. Previously it was thought that light exposure may increase the risk of ROP, but recent research has shown no link.
How do we screen for ROP?
Babies have eye drops put into the eye to dilate the pupils. The ophthalmologist will use an ophthalmoscope or camera to examine the eye. Sometimes they use speculums to keep the eyelid open and an indentor to rotate the eye. It can be uncomfortable, so anaesthetic eye drops are used, or just some trusty sucrose for the baby to suck on.
Basically we want to know where the ROP is (zone) and how bad it is (stage).
There are 3 zones:
- Zone I → surrounding the optic nerve and disc
- Zone II → extending from the edge of zone I to the nasal retina
- Zone III → extending from the edge of zone II to the temporal retina
There are 5 stages:
- Stage I → mildly abnormal blood vessel growth (usually improve with no treatment)
- Stage II → moderately abnormal blood vessel growth (usually improve with no treatment)
- Stage III → severely abnormal blood vessel growth towards centre instead of along retinal surface (sometimes may progress to disease)
- ‘Plus disease’ → if blood vessels become enlarged or twisted (treatment considered)
- Stage IV → partial retinal detachment (treatment required)
- Stage V → complete retinal detachment (end stage disease – treatment required)
How do we treat ROP?
Treatment technique focuses on scarring the peripheral retina to halt abnormal vessel growth and retinal detachment. The central area is preserved, to protect central vision. As a result, there may be some loss of peripheral vision.
There are different types of treatment:
- Laser surgery → most common, usually under sedation or general anaesthetic (GA), and involves laser beams scarring the peripheral retina
- Anti-VEGF injections → newer treatment that can be an alternative treatment or alongside laser therapy, and can be done under local anaesthesia. It promotes normal angiogenesis but more research is needed on long-term outcomes
- Scleral buckling → for later stages of ROP and done under GA. Involves placing a flexible silicone band around the eye, causing it to “buckle” the detached retina outwards towards the wall of the eye
- Vitrectomy → for later stages of ROP and done under GA. Involves replacing the vitreous humour with saline, with the aim of removing scar tissue, to help relieve pressure on the retina.
It’s good to have general knowledge about ROP, especially so that you’re armed with info for any inquisitive parents of preemies. Here are a couple of good info leaflets for parents –
And for your day to day practice, remember the screening criteria so that no baby misses an opportunity to have the treatment they might need.
ROP screening is an important aspect of clinical care in preemies – failure to screen or treat it can threaten visual loss in these babies which we absolutely never want. So make sure whenever you have a preemie deliver in your unit, check if they fulfil the criteria and get them booked in for ROP screening! Iris my case 😉
Key learning points
Dr Arameh Aghababaie, NICU ST2, Dr Hesham El Sayed, Consultant Neonatologist, Newham University Hospital, London