Children born extremely prematurely face up to a 19 times greater risk of retinal detachment later in life than peers born at term, a study in the US journal Ophthalmology said Thursday.

In the first large population-based, long-term investigation of the association between preterm birth and later retinal detachment, researchers determined that birth before 32 weeks is associated with increased risks of retinal detachment in childhood, adolescence and young adult life.

The findings indicate the need for ophthalmologic follow-up in children and adults born extremely and very prematurely, the researchers said.

The researchers used Swedish nationwide population registries of more than 3 million births from 1973 to 2008 to identify subjects born prematurely, who were then separated into two groups: those born between 1973 and 1986, at which point a national retinopathy of prematurity (ROP) screening program was established, and those born between 1987 and 2008.

According to the study, ROP is a condition that causes abnormal blood vessels to grow in the retina (back of the eye) and can cause retinal detachment, which is a major cause of childhood blindness globally.

For those born less than 28 weeks of gestation between 1973 and 1986, the researchers found the risk of retinal detachment was 19 times higher than peers born at term. Those born extremely prematurely between 1987 and 2008 had a nine-fold increase in risk.

Those born 28 to 31 weeks of gestation between 1973 and 1986 had a four-fold increased risk and those born very prematurely between 1987 and 2008 had a three-fold greater risk than those born at term.

However, the researchers found that moderately preterm birth, or 32 to 36 weeks of gestation, was not associated with an increased risk of retinal detachment.

"We may just be seeing the tip of the iceberg of late ophthalmic complications after preterm birth," Anna-Karin Edstedt Bonamy, pediatrician at Karolinska Institutet in Stockholm and the study's lead researcher, said in a statement.

"Not only does the risk of retinal detachment increase with age, but there has also been an increase in survival among people born prematurely since the 1970s. This provides opportunities for future research to address if the increased risk persists among those born prematurely as they age," Bonamy said.