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Overview of Isolated Retinal Neovascularization (IRNV):
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IRNV, previously termed “popcorn” lesions, is a common finding in stage 2 and 3 retinopathy of prematurity (ROP), visualized as neovascular tufts posterior to the ridge.
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Pathophysiology: Driven by low birth weight (BW), low gestational age (GA), and high/fluctuating oxygen exposure, leading to abnormal retinal neovascularization.
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Epidemiology and Risk Factors:
IRNV Demographics: Occurs in higher-risk infants with lower BW (660.1 vs. 916.8 g, P=0.001) and lower GA (24.9 vs. 26.1 weeks, P=0.01).
Zone I Predominance: IRNV strongly associated with Zone I ROP (63.4% vs. 15.8%, P<0.001), indicating more posterior, severe disease.
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Imaging and Diagnosis:
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Ultrawidefield OCT (UWF-OCT):
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Captures >140° en face scans, providing high-contrast visualization of IRNV compared to traditional fundus photography.
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Identifies IRNV morphologies: isolated tufts, coalescent NV separate from the ridge, or confluent NV merging with the stage 3 ridge.
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IRNV Detection: Found in 37% (22/60) of infants with stage 2 or worse ROP in a single-center study.
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Clinical Significance:
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Disease Progression:
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IRNV as a Risk Factor: Independently associated with progression to stage 3 (68.2% vs. 13.2%, P<0.001) and treatment-requiring ROP (54.5% vs. 15.8%, P=0.002), even when controlling for GA, BW, and Zone I disease.
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IRNV often precedes stage 3 by ~2.5 weeks (range 0–8 weeks), appearing at a mean postmenstrual age of 35 weeks.
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Vascular Severity Score (VSS):
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Eyes with IRNV have higher peak VSS (5.61 vs. 3.73, P<0.001) and elevated VSS throughout the disease course, particularly at postmenstrual ages 34–37 weeks (4.02 vs. 3.03, P=0.01).
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Morphological and Longitudinal Features:
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IRNV Location: Predominantly temporal (100%), with nasal involvement in 22.7% and all-quadrant involvement in treatment-requiring cases.
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Recurrence Post-Treatment: IRNV can redevelop after initial regression following intravitreal bevacizumab, requiring subsequent laser for persistent avascular retina.
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3D OCT Evaluation: UWF-OCT provides volumetric analysis of IRNV, potentially serving as a biomarker for disease burden.
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Treatment Implications:
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Anti-VEGF and Laser:
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Of 18 infants requiring treatment, 8 received intravitreal bevacizumab followed by laser for persistent avascular retina.
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IRNV presence increases likelihood of needing intervention, highlighting its prognostic value.
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Monitoring: Eyes with IRNV require closer follow-up due to higher risk of progression and reactivation.
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Future Directions:
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OCT-Based Classification: IRNV’s association with severe ROP suggests potential for integration into future ICROP classifications.
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Research Needs: Longitudinal studies to clarify IRNV’s role in ROP regression vs. progression and its response to therapies.
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Citation
Burt SS, Woodward M, Ni S, et al. Isolated Retinal Neovascularization in Retinopathy of Prematurity: Clinical Associations and Prognostic Implications. Ophthalmology Retina. 2024;8(10):1021-1028. doi:10.1016/j.oret.2024.04.026
