Quantitative reference map of retinopathy of prematurity improves diagnostic reliability and treatment decisions.

BACKGROUND/AIMS: Retinopathy of prematurity (ROP) zone classification guides disease severity assessment and Early Treatment for Retinopathy of Prematurity (ETROP)-based treatment decisions but remains subjective, particularly in the peripheral retina. We developed and validated an anatomically derived quantitative ROP zone reference map to standardise zone assessment in wide-field paediatric retinal images. METHODS: A reference map was constructed using optic disc-fovea distance and multimodal anatomical data, then applied to RetCam panoramic images generated with a robust deep learning registration pipeline. Four ophthalmologists evaluated 85 ROP examinations with and without the reference map in a crossover reader study. Reader-reference and interobserver agreement for zone classification and zone-dependent ETROP decisions were assessed using kappa statistics. RESULTS: The reference map improved reader-reference agreement for zone classification from 0.58 to 0.92 and interobserver agreement from 0.47 to 0.86. In a Zone III versus non-Zone III analysis, reader-reference agreement improved from 0.40 to 0.88. In 20 zone-dependent ETROP observations, agreement improved from 0.85 to complete concordance within this subset. CONCLUSION: The quantitative ROP zone reference map improved reliability of zone classification and supported more consistent ETROP guideline application in this retrospective reader study.