What is the 4-2-1 rule for severe NPDR?

Severe NPDR (4-2-1 rule): ≥4-quadrant intraretinal hemorrhages/microaneurysms, OR ≥2-quadrant venous beading, OR ≥1-quadrant IRMA (intraretinal microvascular abnormality); 1-year risk to PDR: ~15%; high-risk PDR: ~75% vision loss without treatment.

When is panretinal photocoagulation (PRP) indicated?

PRP is indicated for high-risk PDR (NVD >1/4 disc area, any NVD with vitreous hemorrhage, NVE >1/2 disc area with vitreous hemorrhage) and may be considered for severe NPDR in patients with poor follow-up compliance.

When is anti-VEGF preferred over PRP for PDR?

Anti-VEGF (ranibizumab, bevacizumab) achieves non-inferior PDR treatment to PRP with less peripheral VF loss; preferred when DME co-exists with PDR (single agent treats both); PRP is definitive in unreliable follow-up patients.

What HbA1c improvement reduces diabetic retinopathy risk?

DCCT/UKPDS: each 1% reduction in HbA1c reduces retinopathy risk by ~35%; tight control (HbA1c <7%) vs conventional care reduces 10-year retinopathy incidence by 63%; early worsening can occur with rapid HbA1c reduction.

What screening intervals are recommended for diabetic retinopathy?

Type 1 DM: first screening at 5 years after diagnosis; Type 2 DM: at diagnosis; annual screening if no DR; mild NPDR: every 6-12 months; moderate NPDR: every 3-6 months; severe NPDR or PDR: every 1-3 months.

Diabetic Retinopathy Severity Grading (NPDR/PDR)

Grades diabetic retinopathy severity using ETDRS International Classification (mild/moderate/severe NPDR, PDR), calculates 1-year progression risk, and guides panretinal photocoagulation and anti-VEGF injection thresholds.

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