It's a mystery. The eye disease known as retinopathy of prematurity (ROP) can make infants permanently blind if it is not treated. But there are big differences between how often Norwegian hospitals actually provide this treatment.
"These differences between the hospitals are inexplicable," says Dordi Austeng.
Austeng is a professor at the Department of Neuromedicine and Movement Science at the Norwegian University of Science and Technology (NTNU). In fact, the proportion of newborns who develop this condition should be the same across the country.
"There should be no differences between hospitals in the proportion of premature babies who get this disease, and who therefore need to be treated. But there is," she said.
Studied all specialists in Norway
But the unexplained often only needs a thorough investigation before it becomes explainable, and it was precisely such a study that Austeng and colleagues conducted.
Norwegian ophthalmologists were tested to find out whether they are the reason behind the regional differences in eye disease in premature infants.
Could there be a difference between the ophthalmologists at the different hospitals? And that the variation was simply due to how ophthalmologists decided that the eye disease was so serious that it needed to be treated?
"In our study, Norwegian ophthalmologists were tested to find out whether they are the cause of the regional differences in eye disease in premature babies," Austeng said.
All 15 ophthalmologists who examine children in Norway and decide whether or not to treat children participated in the study. The question was whether specialists at some hospitals are stricter than others.
But first, a little about the condition.
Stevie Wonder had this disease
"Incubator blindness" is an old name for the eye disease. Today, professionals most often use the abbreviation ROP, which stands for Retinopathy of Prematurity. The condition usually affects premature babies.
"The blood vessels in the retina that line the inside of the eye are not fully grown in premature babies. The risk of blood vessels growing incorrectly increases the earlier you are born and with oxygen therapy, among other things," said Tora Sund Morken, who is also a professor in the Research Group for Ophthalmology.
Stevie Wonder was born prematurely. He was an incubator baby in the early 1950s, and became blind precisely because of this eye disease.
"Today, fortunately, very few children go blind, as they are examined weekly by specialized ophthalmologists and treated if they are at risk of becoming blind," says Morken.
Most treatment where doctors were strictest
But it is important to get the diagnosis. Hence the thorough examination of the specialists at the hospitals.
"The doctors logged on to a website and completed a test that colleagues in the US have helped us set up," says Austeng.
The doctors thus made this diagnosis less often where the treatment was most common!
The results provided a very unexpected answer.
"The results showed that the ophthalmologists in the region that treated the most children were most restrictive in making the diagnosis of ROP that would require treatment," Austeng said.
The doctors thus made the diagnosis less often where the treatment was most common!
"This is the exact opposite result than what we expected if the ophthalmologists had overtreated the children," says Austeng.
So what on earth is the reason for these differences between the hospitals?
Could it be due to survival rates or lung disease?
"Unfortunately, we don't know the answer yet," says Austeng, but mentions several possible reasons.
There may be differences in survival between hospitals.
"We know that the most premature babies are sicker. This can result in a higher proportion of children with eye disease and more serious eye disease that needs treatment," she said.
Other risk factors are infections or lung disease that require oxygen therapy. It's possible that there are differences between hospitals in the incidence and treatment of these diseases. The research group is still working to figure this out.
Kyrre Moljord is a PhD student on a project that the group has established with Professor Olaf Dammann. Dammann is an epidemiologist from Tufts University in Boston and a visiting professor at NTNU.
Looking for other opportunities
"The next step is to sift through data collected on the children in the Norwegian Neonatal Network," Austeng said.
This network includes records of all newborn diseases, and the treatment they receive from healthcare personnel.
"We hope to find more answers this year. What we know today is that the differences are probably not due to variation in the diagnosis of ROP requiring treatment," Austeng said.
Referanse: Austeng D, Moljord K, Morken TS, Coyner AS, Campbell JP. Inter-observer variability is unlikely to explain regional differences in retinopathy of prematurity in Norway . Acta Ophthalmol. 2026 Apr 24. doi: 10.1111/aos.70146 . Epub ahead of print. PMID: 42032862.
