Panretinal Photocoagulation Indications
Panretinal photocoagulation (PRP) is indicated to reduce the risk of vision loss in patients with high-risk proliferative diabetic retinopathy (PDR) and, in select cases, severe nonproliferative diabetic retinopathy (NPDR). 1
Primary Indications
High-Risk Proliferative Diabetic Retinopathy (PDR)
PRP is most strongly indicated when any three of the following four features are present 1:
- Neovascularization at or near the optic disc (NVD) that is at least one-quarter to one-third disc area in size 1
- Neovascularization elsewhere (NVE) that is at least one-half disc area in size 1
- Vitreous or preretinal hemorrhage in the presence of any neovascularization 1
- Any neovascularization at any location when combined with the above features 1
The landmark Diabetic Retinopathy Study (DRS) demonstrated that PRP reduced severe vision loss from 15.9% in untreated eyes to 6.4% in treated eyes, with the greatest benefit in those with more advanced baseline disease including disc neovascularization or vitreous hemorrhage 1.
Severe Nonproliferative Diabetic Retinopathy (NPDR)
PRP may be considered in select cases of severe NPDR, particularly 1:
- Very severe NPDR defined by the 4-2-1 rule: severe intraretinal hemorrhages in all 4 quadrants, venous beading in 2+ quadrants, or prominent intraretinal microvascular abnormalities (IRMA) in 1+ quadrant 1
- Type 2 diabetes patients with severe NPDR benefit more from early PRP than type 1 patients, with a 50% reduction in severe vision loss or vitrectomy (2.5% vs 5%) 1
- High-risk situations including impending cataract surgery, pregnancy, or poor compliance with follow-up 1
The Early Treatment Diabetic Retinopathy Study (ETDRS) showed that eyes with very severe NPDR have approximately 50% risk of progressing to high-risk PDR within 12-18 months 1.
Important Clinical Considerations
Patient Selection Factors
For Type 1 Diabetes: The timing of PRP depends on patient compliance with follow-up, status of the fellow eye, and presence of pregnancy or impending cataract surgery 1. Deferral until high-risk PDR develops is generally acceptable if close monitoring is feasible 1.
For Type 2 Diabetes: Early PRP before high-risk PDR develops is particularly appropriate, as these patients show greater benefit from early intervention 1.
Anti-VEGF as Alternative
Anti-VEGF therapy (ranibizumab, aflibercept, bevacizumab) is a reasonable alternative to PRP for proliferative diabetic retinopathy 1. The DRCR.net Protocol S demonstrated that ranibizumab was noninferior to PRP at 2 years, with additional benefits including 1, 2:
- Less peripheral visual field loss 1, 2
- Fewer vitrectomy surgeries (4% vs 15%) 1, 2
- Lower risk of developing diabetic macular edema (9% vs 28%) 1, 2
Critical caveat: Anti-VEGF should only be chosen for patients with reliable follow-up, as those lost to follow-up have inferior outcomes compared to PRP 1. Anti-VEGF requires near-monthly injections initially and ongoing treatment 1.
Concurrent Diabetic Macular Edema
When center-involved diabetic macular edema (CI-DME) is present with PDR requiring PRP, combined anti-VEGF therapy and PRP at the first treatment session should be considered 1. PRP can exacerbate macular edema and should not be performed in isolation when significant DME threatens vision 1.
Common Pitfalls to Avoid
- Do not delay PRP when high-risk PDR is present (extensive NVD or recent vitreous/preretinal hemorrhage), even if macular edema is present—treat both concurrently 1
- Do not perform partial or limited PRP—full PRP with 1200-1600 spots is the proven treatment approach 1
- Do not choose anti-VEGF monotherapy for patients with poor compliance or unreliable follow-up—these patients require the durability of PRP 1
- Do not assume pregnancy is a contraindication to PRP—pregnancy accelerates retinopathy progression and PRP can minimize vision loss risk 1