How does retinopathy of prematurity develop?

In this video we consider why and how retinopathy of prematurity (ROP) develops and describe the changes that take place in the retina (in the inner layer of the eye). It is important to remember that ROP only develops in infants born four or more weeks premature and that it is only seen in infants who have received neonatal care.

A brief history of ROP

Blindness from ROP was first decribed in the United States of America (USA) in the 1940s, when it was called retrolental fibroplasia (RLF), which means “a fibrous mass behind the lens.” What the ophthalmologists were seeing was a total retinal detachment and scar tissue. At that time the earlier stages i.e., before retinal detachment, had not been described because equipment was not available then to examine the peripheral retina.

In the 1940s and 50s RFL was the single most common cause of blindness in children in high income countries. During this ‘first epidemic’ of ROP the level of neonatal care was poor and ROP related blindness occurred in larger babies with a birthweight of 1000 – 2000g. There was high mortality in the low birth babies.

In 1952 Szewczyk suggested that misuse of 100% supplemental oxygen given to premature babies, which led to hyperopia (high levels of oxygen in the blood) and sudden episodes of anoxia (lack of oxygen), was a cause of RFL. An increase in the rate (incidence) of RFL cases was seen in hospitals that had introduced incubators with high oxygen concentrations for preterm babies.

By the mid-1950s abundant clinical and experimental data showed that RFL was due to overuse of supplemental oxygen. Studies identified the appropriate levels of oxygen preterm babies required and hospitals began introducing new methods to monitor oxygen levels.

By the 1960s and 70s, in high income countries, most babies who developed severe ROP were born weighing less than 1000g. This was called the ‘second epidemic’ of ROP. In the 1990s, treatment in the form of cryotherapy became available for ROP for the first time, and over the last two decades laser has become the standard treatment.

However, the situation has been and remains different in low- and middle-income countries which have been going through a ‘third epidemic’ of blindness due to ROP since the 1980s (Gilbert et al 1997). This third epidemic is a mixture of the first two epidemics and is characterised by high rates of severe ROP developing in both relatively mature and immature preterm babies, reflecting the varying levels of neonatal care provided (Shah et al. 2009). This is compounded by lack of inadequate screening and treatment services. In high-income settings, most infants developing the severe stages of ROP now have extremely low birthweight (less than 1000g) and high quality screening and treatment means that blindness is largely prevented.

The understanding of ROP and its risk factors continue to evolve, which influences practice. In your experience of neonatal care or ROP services, what are the challenges in keeping up to date with evidence based practice?