What is Retinopathy of Prematurity (ROP)?

Retinopathy of Prematurity (ROP) is a condition found in the eyes of ex-preterm babies. It is characterised by changes in the developing blood vessels of the retina (the light-sensitive layer in the back of the eye that sends visual signals to the brain). Although mostly it resolves without problems, if not identified and treated progressive disease can lead to scarring and retinal detachment (separation of the retina from the inside of the eye), causing poor vision or even blindness.

Who is affected and what are the risk factors?

Many different factors contribute to the development of ROP. Babies born before 31 weeks or less than 1,250g birthweight are at highest risk. The main risk factor is the use of oxygen therapy.  The healthcare teams monitor oxygen levels in the baby very closely and try to find a balance between enough oxygen to prevent other serious diseases and too much, which encourages ROP.  

The occurrence of the disease varies across countries, regions and facilities and is determined by the quality of neonatal care and the resources of the facility.  For example, among babies born in Western countries after 30-32 weeks of gestation, two to nine percent of the babies may develop some grade of ROP. When born at 26 weeks of gestation, the number increases to 50 percent. Those babies born  below 26 weeks are at highest risk and the progression of ROP may be particularly rapid in this group.

What is the cause?

After birth (usually before 30 weeks of pregnancy) the blood vessels stop their normal growth out from the back of the eye, that starts as early as 16 weeks of pregnancy and usually covers the whole retina by 40 weeks of pregnancy (full term).  This leads to poor delivery of oxgen and nutrients to the developing tissue. As the eye recovers from this (usually after 31 weeks of gestation), the new blood vessels may grow in an abnormal manner that can cause major problems.

How is it diagnosed?

All preterm babies born before around 31 weeks of pregnancy or having a birth weight less than 1,250g to 1,500g may have eye examinations to detect the presence of ROP by a specialised eye doctor, called ophthalmologist. Since vessel regrowth starts after a lag period, the first screening usually takes place after four to six weeks following birth and continue until the ophthalmologist is happy that re-growth is complete and any ROP resolved, avoiding the complications that lead to later blindness.

Before screening, the baby receives eye drops to dilate the pupils so the retina can be seen fully. During the examination the child is usually wrapped and held by a parent or nurse to comfort and avoid movement. The procedure is uncomfortable for the babies and they may cry during the examination. Parents may wish to comfort their baby afterwards. Increasingly, the doctors and nurses on the neonatal unit may take photographs of the retina for the ophthalmologist to reduce the number of visits.

How is it managed?

Although most babies do not need treatment, it is very difficult to predict in which babies ROP will disappear and which will develop more severe disease.

This is why it is very important that an ophthalmologist continues with the screening in regular time intervals until the vessels cover the retina or the condition is considered stable. Sometimes, examinations have to continue until a few months after discharge.

If the progression of ROP reaches key stages (threshold) it is very likely that vision is at risk, treatment is warranted. One of three treatments are available:

  • Laser therapy works by destroying the peripheral areas of the retina causing abnormal vessels to disappear. Unfortunately, the treatment also affects later side vision. Treatment is usually given to both eyes and the eyes examined again five to seven days after treatment.

  • Cryotherapy (applying a freezing probe to the outside of the eye to stop vessel re-growth) was the first treatment for ROP but is more difficult to use in very small babies and is used less frequently.

  • More recently, some professionals are using an injection of an antibody to the chemicals that make the blood vessels regrow to treat ROP. This is used widely in adults with similar conditions. In babies, this is at the moment controversial but trials are under way to show how safe and effective it is.


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