Study Shows Impact of Birth Weight on Retinopathy of Prematurity

NICU baby is cared for by hospital staff and mother after premature delivery.
In a nationwide study across South Korea, researchers found associations with higher mortality and visual impairment.

A report shows strong associations between birth weight and the risk of retinopathy of prematurity (ROP) across the South Korean population.1 The research also parsed issues of visual impairment, treatment methods and mortality in these patients.

The investigation used 11 years worth of data culled from the National Health Insurance and the Korean Disability Registry database, which covers the country’s entire newborn population.1 They reviewed the ROP incidence, rate of visual impairment (VI), and mortality in patients with ROP. They divided the premature patients’ records into 3categories according to birth weight. Patients weighing less than 1500 g were considered very low birth weight (VLBW). The next group weighed between 1500 g and 2499 g, and the third group weighed 2500 g.

They found that, in total, 8273 patients were born between 2006 and 2014 with ROP, which is a rate of 1 in 502 newborns. By birth weight, the incidence was approximately 1 in 3 in the VLBW group, 1 in 40 in the 1500 g to 2499 g group, and 1 in 3500 in the group that weighed 2500 g or greater.

Patients in the lowest birth-weight class also had the most cases of visual impairment. Additionally, most of the patients who were found to have visual impairment had severe visual impairment. Visual impairment was monitored for patients born in between 2006 and 2014 up to 2016. A total of 138 were found to have visual impairments, of whom 87 (63%) had a severe case. 

By age 6, the rate of visual impairment in these patients was 1.8 per 100 person-years and 2.2 per 100 person-years by age 10. By birth weight, the visual impairment rate was highest in the VLBW population, 3.7 per 100 person-years at age 6 and 4.5 per 100 person-years at age 10. In the 1500 g to 2499 g group, the impairment rate was 1.0 per 100 person-years at age 6 and 1.3 per 100 person-years at age 10. In the 2500 g or greater group, the rates were 1.7 per 100 person-years at age 6 and 2.1 per 100 person-years at age 10. Of the 138 patients with ROP with visual impairment, 36 (26.1%) had ocular comorbidities, most of which were congenital ocular anomalies.

The investigators also compared the mortality risk between treatment methods, after excluding the infantile deaths in which treatments for ROP were not performed due to poor overall condition. The treatment methods included laser photocoagulation or cryotherapy, intravitreal anti vascular endothelial growth factor (VEGF) injection (with or without laser photocoagulation or cryotherapy), and  vitrectomy or scleral buckling surgery (with or without laser photocoagulation, cryotherapy, or anti-VEGF injection). 

Researchers say the overall mortality rate in ROP in this study was 4.8 per 1000 person-years. “This result suggests that clinicians should consider general medical conditions in babies with ROP, which may lead to death,” the researchers explained.

While patients undergoing any treatment had a higher mortality rate than nontreated patients, the risk of death was similar between treatment modalities. Researchers say this contradicts previous reporting.2 Of those who were treated, the surgically treated patients had the highest proportion of visual impairment. The researchers say they also found a greater association of visual impairment in patients who underwent anti-VEGF treatments than those who received either laser or cryotherapy treatments, even when controlling for age, sex, birth weight, and ocular comorbidities.1 

“Given that both modalities can be performed for nonsurgical indications, this finding suggests a possible difference in long-term visual outcomes between anti-VEGF injection and laser/cryo,” the researchers affirmed.1


1 Na K, Kim K, Kang T, Hann H, Ahn H, Kim H. Incidence, long-term visual outcomes, and mortality in retinopathy of prematurity in korea: a nationwide population-based study. Invest Ophthalmol Vis Sci. 2020;61(10):14. doi: 10.1167/iovs.61.10.14

2. Mintz-Hittner HA, Kennedy KA, Chuang AZ; BEAT-ROP Cooperative Group. Efficacy of intravitreal bevacizumab for stage 3+ retinopathy of prematurity. N Engl J Med. 2011;364(7):603-615. doi: 10.1056/NEJMoa1007374