How is ROP diagnosed and staged?

An instrument called a binocular indirect ophthalmoscope is used to examine for ROP. Eye drops are used to dilate the pupils before examination, allowing for a better view of the retina. A stabilizing device may be used to hold the eyes open during the examination. Photographs of the retina may also be taken.1,2

ROP is classified by describing 3 key features:2,5

  • Zone: refers to the location of retina affected
  • Stage: refers to severity of disease, ranging from stage 1 (mild) through 5 (severe)
  • Appearance of retinal blood vessels: refers to the presence or absence of “plus” disease

Although development of ROP typically occurs in both eyes, each eye may have different zone, stage and plus disease classifications.4,5

Location of the retina: “Zone”

Zone 1 includes the center of the retina, the area of the retina responsible for the clearest, straight-ahead (central) vision. Zones 2 and 3 are each further away and are responsible for side (peripheral) vision. Because of the effect on central vision, ROP is more of a threat to vision in zone 1 than zone 3.5

Severity of disease: “Stage”

There are five stages of severity of ROP. Higher numbered stages represent more severe disease and threat to vision than lower numbered stages.5

Appearance of blood vessels: Evaluating for “plus” disease

ROP is also classified by the shape of the retinal blood vessels. If the vessels begin to take a wavy pattern or appear thicker than normal, plus disease may be present. Plus disease can indicate a worsening of ROP.2,5


  1. Fierson WM, American Academy of Pediatrics Section on Ophthalmology; American Academy of Ophthalmology; American Association for Pediatric Ophthalmology and Strabismus; American Association of Certified Orthoptists. Screening Examination of Premature Infants for Retinopathy of Prematurity. Pediatrics. 2018;142(6):e20183061.
  2. American Association for Pediatric Ophthalmology and Strabismus. Retinopathy of Prematurity. Last updated November 4, 2021.
  3. Subspecialist Eye Associates. Common Eye Tests.
  4. Molinari A, et al. Classifying retinopathy of prematurity. Community Eye Health. 2017;30:55-56.
  5. Chiang MF, Quinn GE, Fielder AR, et al. International Classification of Retinopathy of Prematurity, Third Edition. Ophthalmology. 2021;128(10):51-68.
  6. University of Maryland Medical Center. Retinopathy of Prematurity (ROP).
  7. Safer Care Victoria. Retinopathy of prematurity (ROP). Last updated February 17, 2021.
  8. Bozell C. Normal fundus image. Retina image bank. 2018;28545.
  9. Ells AL. Stage 3 ROP. Retina Image Bank. 2018;28486.

All URLs accessed 7/6/22.

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Scientific Council

Neil M. Bressler, MD

James P. Gills Professor of Ophthalmology
Professor of Ophthalmology, Johns Hopkins University School of Medicine
Wilmer Eye Institute, Johns Hopkins Medicine
Baltimore, MD

A. Paul Chous, MA, OD, FAAO

Specializing in Diabetes Eye Care & Education, Chous Eye Care Associates
Adjunct Professor of Optometry, Western University of Health Sciences
AOA Representative, National Diabetes Education Program
Tacoma, WA

Steven Ferrucci, OD, FAAO

Chief of Optometry, Sepulveda VA Medical Center
Professor, Southern California College of Optometry at Marshall B. Ketchum University
Sepulveda, CA

Julia A. Haller, MD

Wills Eye Hospital
Philadelphia, PA

Allen C. Ho, MD, FACS

Director, Retina Research
Wills Eye Hospital
Professor and Chair of the Department of Ophthalmology
Thomas Jefferson University Hospitals
Philadelphia, PA

Charles C. Wykoff, MD, PhD

Director of Research, Retina Consultants of Houston
Associate Professor of Clinical Ophthalmology
Blanton Eye Institute & Houston Methodist Hospital
Houston, TX



Patient & Caregiver Educational Resources

The RELIEF Patient Toolkit is a blindness prevention resource center for caregivers of infants who have been diagnosed with or those who are interested in educating themselves about retinopathy of prematurity (ROP). Choose from the options below to learn more.

This activity is provided by Med Learning Group. This activity is co-provided by Ultimate Medical Academy/Complete Conference Management (CCM). This activity is supported by an independent medical education grant from Regeneron Pharmaceuticals, Inc.

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