Perelman School of Medicine at the University of Pennsylvania

Center for Preventive Ophthalmology and Biostatistics (CPOB)

The Postnatal Growth and Retinopathy of Prematurity (G-ROP) Studies

The G-ROP studies are two large-scale multi-center studies, sponsored by the National Eye Institute, to develop a ROP prediction model on a retrospective cohort (n=7,483) and validate the prediction model on a prospective cohort (n=4,393) using postnatal weight gain to identify infants with severe ROP.

Why is it important?

Retinopathy of prematurity (ROP) is a blinding disease of the developing retinal vasculature. Clinical management includes serial retinal examinations of at-risk infants and treatment with laser retinal photocoagulation or intravitreal injection of an antivascular endothelial growth factor agent to reduce the risk of progression to retinal detachment. Current ROP screening criteria are based on birth weight (BW) and gestational age at birth (GA) (eg, in the United States, BW < 1501 g or GA ≤ 30 weeks). Approximately 70 000 infants a year in the United States alone receive examinations.

The current screening criteria have low specificity for predicting which infants are at risk for severe ROP; only 5% to 10% of infants who are examined require treatment.  In addition, while their sensitivity for predicting severe ROP is very high, it is not 100%, as larger-BW and older-GA infants sometimes require treatment, and the guidelines include a third, poorly defined screening criterion for larger-BW, older-GA infants with a poor postnatal course in the judgement of the neonatologist. Therefore, there are opportunities to improve both the specificity and sensitivity of these criteria if risk factors for ROP other than BW and GA could be applied in a more systematic manner.

Postnatal weight gain–based models improve specificity but have been limited by complexity and small development cohorts, which results in model overfitting and resultant decreased sensitivity in validation studies.

G-ROP Studies aim to develop and validate a new BW, GA, and postnatal weight gain ROP model using data from diverse cohorts of at-risk infants in North America to provide precise estimates of sensitivity and to make the risk model simple enough to be applied clinically.

Study Design

The G-ROP studies consisted of two similarly-designed studies: a retrospective cohort study for developing a prediction model using postnatal weight gain to identify infants who are likely to develop severe ROP, and a prospective cohort study to validate the model in a diverse cohort of at-risk infants. The retrospective cohort study enrolled 7,483 infants (born between January 1, 2006, and December 31, 2011) at 29 hospitals in the U.S. and Canada. Eligible infants were those who underwent ROP exams, without any BW or GA restrictions, and had a known ROP outcome. Certified data abstractors collected detailed ophthalmologic and medical data, including BW, GA, daily postnatal weight measurements, supplemental oxygen use, platelet counts, weekly nutrition, medical events, and all ROP exam findings.

The prospective cohort study enrolled 4,393 infants (born between May 23, 2015 to May 15, 2017) from 41 hospitals in the U.S. and Canada, with 25 hospitals that participated in the retrospective study for temporal model validation and 16 new hospitals for external validation. Certified coordinators prospectively collected detailed ophthalmologic and medical data, including demographics, ROP and daily weight measurements. Demographic, ROP, weight, and oxygen data collection was the same for both studies.

G-ROP Publications:

Click here for a list of G-ROP publications

CPOB's Role in G-ROP:

The CPOB serves as the Data Coordinating Center  for the G-ROP Studies.