Retinopathy of prematurity; how ROP affects a baby’s vision and how to treat it.

What is ROP or retinopathy of prematurity? 

ROP is a condition that affects the developing retina in babies who have been born severely prematurely, or at very low birth weights. Mr Robert Henderson, leading consultant paediatric ophthalmologist talks about ROP, how it affects a baby’s vision and what can be done to treat it.

A baby’s retinal blood vessels start developing at 16 weeks when they come out of the optic nerve at the back of the eye. They then start to run along the inner surface of the retina where they reach the periphery of the retina by 37 weeks of pregnancy. When babies are born very prematurely, the most important thing that the baby requires is oxygen delivered through its lungs which are immature and poorly developed at this young age, rather than the umbilical cord.

Doctors have to increase the oxygen delivered to the baby in order to supply the baby’s developing brain, but unfortunately, this high amount of oxygen can impede the growth of retinal blood vessels. This in turn can cause new, fragile and abnormal blood vessels to grow out of the retina which, in turn, frequently break and bleed. If left untreated, these blood vessels will scar and shrink and start to pull the retina apart. This leads to retinal detachment and quite often, blindness.

Are there different stages of ROP?

There are 5 stages of ROP, which vary in degrees of severity. When babies are screened for retinopathy of prematurity, they are screened according to certain guidelines. The developing blood vessels and any ROP are graded according to the stage of severity (stages 1-5) and according to the location in the retina (zones 1-3). A final factor known as plus disease is also tested for and is the most important indicator of whether to baby should be treated for ROP or not. Stage 4 and 5 ROP are the most severe and lead to retinal detachment.

How does ROP affect a baby’s vision? 

Mild ROP that does not need treatment often has little impact on vision. That being said, babies born prematurely or who have ROP do have a higher incidence of needing glasses and developing a squint (turning eye). If significant ROP develops, however, and laser is required, then there is a very high risk that the baby will develop significant short-sightedness in the coming years, with the need for glasses to correct this. Stage 4 and 5 retinal detachments are associated with significant visual impairment and even blindness.

What causes ROP?

The main factors that are known to cause ROP include:

• Prematurity: babies born at 23-25 weeks are far more likely to develop ROP than babies born at 30 weeks.
• Low birth weight is another very important factor. Babies weighing 500g are much more likely to develop ROP than those weighing 1400g.
• Finally, though there are a number of other factors known to influence development, exposure to high amounts of oxygen in the early weeks, post premature delivery, carries a very significant risk of causing ROP.

How can ROP be treated? 

• Laser: The primary and gold standard treatment for ROP remains laser. This is applied to the peripheral retina where no blood supply has developed. The aim of laser is to turn off the production of a chemical message produced by the retina called Vascular Endothelial Growth Factor (VEGF); it is this molecule that drives the formation of damaging blood vessels. 
• Blocking antibodies: Blocking antibodies have been designed, that are ‘anti-VEGF’, and can be injected into the eye to turn off VEGF production. These are very effective and are sometimes used in the UK in specific circumstances. The problem is that the anti-VEGF molecules leak out of the eye and may turn off VEGF production in the developing brain amongst other organs, where it is actually needed. We do not yet know the effect that these antibodies have on development and what the long-term dangers are, hence doctors are very cautious about using them as treatment.
• Surgery: If the retina detaches, babies are sent to Great Ormond Street from across the U.K to be treated by the vitreous-retinal surgical team there. The aim is to cut the ‘tractional bands’ formed by the scarring blood vessels that are pulling the retina apart. This is one of the only places in the world that uses a tiny fiberoptic camera inside the eye to look at and cut the bands.

If left untreated, what problems will this have for the baby? 

Retinopathy of prematurity, if left untreated, will frequently progress to stage 4 or 5 retinal detachment and subsequent blindness or severe visual impairment. This has a huge developmental impact on the child who no longer has vision with which to reach out and grab objects or to explore the world with. Very often, these very premature babies have a number of other cognitive or physical problems, and blindness only increases the burden both on the child, their family and on society who will have to provide care and support for the child for a life time.