Decoding the Report: Zones, Stages, and Plus Disease

When the ophthalmologist finishes an eye exam in the NICU, they use a specific “medical shorthand” to describe what they saw. This standardized language, updated in the latest ICROP3 (International Classification of Retinopathy of Prematurity) guidelines, helps the entire care team understand how severe the condition is and how quickly they need to act ^[1].

Understanding these three main categories—Zones, Stages, and Plus Disease—will help you follow your baby’s progress and participate in care decisions.

The Three Zones: Location Matters

Think of the retina as a target with the optic nerve at the center. The “Zone” tells the doctor where the abnormal blood vessels are located ^[1].

• Zone I (The Center): This is the most central area, closest to the optic nerve. ROP in Zone I is considered more serious because it affects the most critical part of the retina ^[1][2].
• Zone II (The Middle): This is a ring around Zone I. It is the most common area where ROP is found ^[1].
• Zone III (The Edge): This is the outer “crescent” at the very edge of the eye. ROP here is generally the least severe ^[1].
• The Rule: The lower the Zone number, the more concerned doctors are, as the disease is closer to the center of vision ^[1][2].

The Five Stages: Severity of Growth

The “Stage” describes the appearance of the abnormal vessels where they meet the “empty” part of the retina ^[1][3].

1. Stage 1 (Demarcation Line): A thin, flat white line separates the normal vessels from the area without vessels.
2. Stage 2 (The Ridge): The line grows into a raised ridge, like a small step.
3. Stage 3 (Overgrowth): Abnormal vessels begin to grow out of the ridge and into the gel-like center of the eye (vitreous). This is a sign of active, aggressive growth ^[1].
4. Stage 4 (Partial Detachment): The abnormal vessels pull on the retina, causing it to partially lift away from the back of the eye ^[3].
5. Stage 5 (Total Detachment): The retina is completely detached, which is a medical emergency for vision ^[1][3].

Plus Disease: The Red Flag

Plus Disease is perhaps the most important term in the report. It means the blood vessels in the back of the eye have become significantly swollen (dilated) and twisted (tortuous) ^[1][4].

• Plus Disease: A sign that the disease is very active and likely needs treatment quickly ^[5][6].
• Pre-plus Disease: The vessels are starting to look abnormal but don’t yet meet the full criteria for “plus.” This means the baby needs very close monitoring ^[7][8].

Putting It Together: Type 1 vs. Type 2

Doctors use the Zone, Stage, and Plus status to categorize ROP into two main types:

• Type 1 ROP (Treatment-Requiring): This is a “high-risk” state where the risk of vision loss is high enough that treatment (like laser or injections) is recommended immediately ^[2][9].
• Type 2 ROP (Close Monitoring): This is a “watchful waiting” state. The ROP is significant, but it doesn’t yet meet the criteria for treatment. These babies are screened very frequently (often every few days) to see if they progress to Type 1 or begin to heal ^[2][9].

A Note on Aggressive ROP (A-ROP)

In rare cases, ROP doesn’t follow the normal stages. Aggressive ROP (A-ROP) is a severe form that moves very quickly and can lead to retinal detachment if not treated urgently, often within 48 to 72 hours ^[1][10]. Because it moves so fast, it requires the highest level of medical attention ^[11].

Quick Checklist: Questions for the Eye Doctor

After each exam, ask your doctor these three questions to stay informed:

• What Zone and Stage is my baby currently in?
• Are there any signs of “Plus Disease”?
• Is my baby classified as Type 1 or Type 2?