Icrop3 guidelines and changes
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ICROP3 International Classification of Retinopathy of Prematurity third edition 2021 changes guidelines
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https://pmc.ncbi.nlm.nih.gov/articles/PMC10979521
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PMID: 34247850
ICROP3: key guidelines and changes
ICROP3 is the 2021 third edition of the International Classification of Retinopathy of Prematurity. It is primarily a standardized classification and reporting system, not a new screening or treatment guideline. It retains the core descriptors:
- Zone: location of disease
- Stage: morphology at the vascular-avascular junction
- Extent: clock hours involved
- Plus disease: posterior vascular activity
The full consensus statement is available in the ICROP3 publication.
How to document an eye under ICROP3
Record, for each eye:
Zone + stage + extent (clock hours) + vascular status (no plus, pre-plus, plus) + whether aggressive ROP is present.
Also document regression, reactivation, and persistent avascular retina when applicable.
Example:
Right eye: Zone II, stage 3, 5 clock hours, plus disease, no A-ROP.
What changed from ICROP 2005 to ICROP3?
| Area | ICROP3 update | Practical meaning |
|---|---|---|
| Zone II | Introduces the term posterior zone II | Identifies more posterior disease within zone II, which often carries higher risk than anterior zone II disease. |
| Notch | A notch is disease extending 1-2 clock hours into a more posterior zone | Avoids wrongly labeling an eye solely by its predominant zone when a small posterior extension is present. |
| Plus disease | Recognizes a continuum from normal vessels to pre-plus to plus disease | Vascular dilation and tortuosity should not be viewed as simply present or absent. Clinical judgment and serial comparison matter. |
| Aggressive disease | Aggressive ROP (A-ROP) replaces aggressive-posterior ROP (AP-ROP) | Aggressive disease can occur outside the posterior retina and in larger preterm infants, especially in settings with limited neonatal resources. |
| A-ROP definition | Emphasizes rapid progression, marked plus disease, flat neovascularization, and often an ill-defined ridge | The key feature is aggressive behavior and vascular abnormality, not only posterior location. |
| Stage 5 | Stage 5 retinal detachment is subdivided into 5A, 5B, and 5C | Gives a more useful description of funnel configuration and anterior segment involvement. |
| Regression | Formal description of spontaneous or treatment-associated regression | Helps distinguish inactive/regressing disease from persistent active ROP. |
| Reactivation | Formal definition and reporting recommendations | Particularly relevant after intravitreal anti-VEGF treatment, where recurrent activity may occur later. |
| Persistent avascular retina | Recognized and should be described by zone and extent | May persist after regression, especially following anti-VEGF therapy, and requires ongoing surveillance. |
| Imaging | Incorporates the role of wide-field imaging, fluorescein angiography, and OCT/OCT-A where available | Imaging supports documentation and monitoring but does not replace a skilled clinical examination. |
| Long-term sequelae | Adds standardized description of late retinal and ocular consequences | Includes retinal detachment, retinal breaks, retinoschisis, macular abnormalities, vascular changes, and glaucoma. |
The terminology updates are summarized in the original ICROP3 abstract.
Stage 5 subcategories
- Stage 5A: total retinal detachment with an open funnel
- Stage 5B: total retinal detachment with a closed funnel, but posterior structures can still be visualized
- Stage 5C: closed funnel with anterior segment involvement, such as lens displacement, shallow anterior chamber, or corneal opacity
Important clinical points
1. A-ROP is not limited to Zone I
The older label, AP-ROP, implied that the condition was necessarily posterior. ICROP3 changes this to A-ROP because aggressive disease may occur beyond posterior zone II.
2. Regression is not necessarily cure
After disease regresses, document:
- whether vascularization has reached the periphery
- the location and extent of any persistent avascular retina
- whether there are residual vascular or vitreoretinal changes
3. Reactivation is especially relevant after anti-VEGF therapy
Anti-VEGF agents may produce apparent regression but can be followed by delayed recurrent disease. Therefore, follow-up must be prolonged and individualized.
4. ICROP3 does not create a new treatment threshold
Commonly used treatment decisions still follow ETROP Type 1 ROP criteria:
- Zone I, any stage with plus disease
- Zone I, stage 3 without plus disease
- Zone II, stage 2 or 3 with plus disease
ICROP3 helps describe the disease more precisely but does not replace local ROP screening, examination, or treatment protocols.
Examination reminder
A standard ROP assessment should state:
- Most posterior zone
- Highest stage
- Extent in clock hours
- No plus / pre-plus / plus
- A-ROP present or absent
- Regression, reactivation, and persistent avascular retina, if relevant
Kanski’s summary similarly describes ICROP3 as using zone, stage, and active vascular features, while defining a notch as a 1-2 clock-hour incursion into a more posterior zone. Kanski’s Clinical Ophthalmology, 10th ed., ROP section.
Bottom line: ICROP3 modernizes ROP nomenclature for posterior disease, vascular severity, aggressive ROP, post-treatment regression/reactivation, and late sequelae. It improves documentation and communication, especially in the anti-VEGF era.
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