retinopathy of prematurity

retinopathy of prematurity

Retinopathy of Prematurity (ROP) is a condition which affect babies who are born prematurely with the consequence of inadequate or abnormal retinal vessel development. As a result, the retina does not develop properly and thus cannot work properly. This affects the childs' development and can range from completely normal vision to complete blindness depending on the severity of the condition. Not all babies who are born prematurely develop ROP and fortunately most (approx. 90%) with ROP only have the milder form of the condition. 

what causes rop?

Retinopathy of Prematurity (ROP), as the name implies, is caused by the baby being born too early and/or not heavy enough. Like the rest of the body, the eye too develops during pregnancy and the vessels grow out from the optic nerve (see Normal Anatomy), branching radially until it reaches the edge of the retina. The retina develops as this process occurs and it is halted for any reason, then it may stop developing (Fig. 1). 

Figure 1. Photo Montage of ROP showing demarcation line between developed and undeveloped retina (blue arrows)

how do you detect rop?

Your child's Paediatrician or your Gynaecologist will be able to advise you on this depending on your child's birth-weight and how early s/he is when s/he was born. In general the Malaysian guidelines advocate screening for ROP by a qualified Ophthalmologist if the:

 

  • Birth weight is less than 1500g

  • Gestational age is less than 32 weeks or

  • Infants have an unstable clinical course (as determined by your Paediatrician / Neonatologist)

 

These are guidelines however there are many situations in which screening may be advocated for babies outwith these guidelines (for example even if they were born at 34 weeks or 1700g) they may require screening.

 

Screening entails an examination by an eye doctor at an appropriate time when the baby is well enough to undergo an eye examination. S/he will require eye drops to dilate the pupils so that a full examination of the retina can be undertaken. This may require the use of a speculum (wire-clip to open the eyes) and a scleral depressor (to check the peripheral retina). Local anaesthetic eyedrops will be placed so that your baby doesn't feel pain however they will usually still cry a lot and fight it (as you would expect). This is normal but we will ensure they are properly monitored during this process so that we know if we need to stop. (Fig. 2)

 

The screening is usually done at regular intervals until the retina is fully developed and may start even whilst they are still in hospital. We understand there may be many (cultural) restrictions to bringing very young babies out of the house at this young age however it is imperative they get their eyes checked at the appropriate time as otherwise complications can result which may permanently affect their vision for the rest of their lives. 

Figure 2. Screening for ROP in a neonate.

(Image courtesy of NIH National Eye Institute)

what are the complications of rop?

ROP is broadly classified into 5 stages which ranges from mild (Stage I) to very severe (Stage V). From stage III onwards, new, abnormal blood vessels develop in the retina. Though it sounds good, these blood vessels actually have the potential to do more damage than good as they are more fragile and leaky than our normal vessels. They also tend to scar up and cause retinal detachments (Stages IV & V). The aim is to avoid new blood vessels developing with targeted laser treatment as described below. Even if new blood vessels develop, it is still possible to treat it with laser treatment or an injection of some medication into the eye or retinal surgery. As with anything however, it is always best to catch the disease process at the earliest possible to try and achieve the best outcome which is why screening is so important. 

how rop is treated?

If ROP is detected, the aim is to encourage normal retinal vascular development and this will require a team effort with coordination between your Paediatrician or Neonatologist, Ophthalmologist and most importantly yourselves as parents. The child needs to have very controlled oxygen therapy if required - not too much or too little and his/her general health status needs close monitoring. 

 

If treatment is required, it should be performed promptly. The types of treatment available include laser to the unhealthy retina. Some doctors may opt for freezing treatment (cryotherapy) instead however studies have shown that laser yields better outcomes in the long-term. Recently it has also been shown that injection of an anti-Vascular Endothelial Growth Factor (anti-VEGF) reduces the growth of abnormal blood vessels in a subset of babies whose disease can't be controlled with laser alone. If however it reaches this stage of severity, your eye doctor will explain all the risks and benefits of such treatment as, currently, it is still not licensed for use in children. It is also prudent to have a retinal surgeon to assess your child at this stage as injections in this age group are very different from adults and if things do happen to take a turn for the worse, s/he may require retinal surgery at very short notice. 

what are the long term effect?

Regardless of whether the ROP was well-treated or not, it is always wise to have an annual check-up with your eye doctor if your child had been diagnosed with ROP in the past. This is because infants with ROP are at higher risk of developing certain eye problems later on in life. This includes (but is not limited to): 

 

  • Squint (Crossed eyes)

  • Myopia (Short-sightedness)

  • Amblyopia (Lazy Eye)

  • Glaucoma

  • Retinal tears / retinal detachment

  • Vitreous haemorrhage (bleeding in the eye)