What is the optimal way to treat an adult with proliferative diabetic retinopathy requiring pan‑retinal photocoagulation?

Optimal Treatment Approach for Proliferative Diabetic Retinopathy Requiring Panretinal Photocoagulation

For adults with high-risk proliferative diabetic retinopathy requiring panretinal photocoagulation, full PRP using 1200-1600 laser spots remains the proven standard treatment, though anti-VEGF therapy (ranibizumab or aflibercept) is a reasonable alternative specifically for patients with reliable follow-up who can commit to frequent monitoring and injections. 1

Primary Treatment Decision Algorithm

When to Choose Traditional PRP:

• Patients with uncertain follow-up compliance - This is the critical deciding factor, as patients lost to follow-up after anti-VEGF therapy have significantly worse visual and anatomic outcomes compared to those who received PRP 1
• High-risk PDR requiring expeditious treatment - Most patients with high-risk characteristics (extensive neovascularization of the disc or vitreous/preretinal hemorrhage) should receive PRP promptly 1
• Patients preferring fewer treatment visits - PRP typically requires 1-3 sessions versus monthly injections for anti-VEGF 1

When to Choose Anti-VEGF Therapy:

• Patients with reliable follow-up who can commit to frequent monitoring 1
• Concurrent center-involving diabetic macular edema - Anti-VEGF addresses both proliferative disease and macular edema simultaneously 1
• Concern for peripheral visual field preservation - Anti-VEGF patients experience less peripheral vision loss than PRP 1
• Risk of worsening macular edema from PRP 1

Technical Specifications for PRP Execution

Standard ETDRS Protocol (Proven Effective):

• 1200-1600 laser spots of moderate intensity 1
• 0.1 second duration per burn 1
• Spacing: one-half burn width apart 1
• Coverage: at least 2 disc diameters from fovea extending to the equator 1
• Full PRP is proven; partial or limited PRP is not 1

Modern Pattern Scan Laser (PASCAL) Alternative:

• Single-session delivery is feasible and effective using 20-millisecond duration burns 2, 3
• Approximately 1500-2885 burns can be safely delivered in one session 2, 4
• Significantly shorter treatment time (5 minutes versus 59 minutes for conventional multi-session) 2
• Similar efficacy to conventional argon laser with comparable regression rates 5, 2, 4
• Higher power settings required (650 mW versus 330 mW for conventional) but with acceptable safety profile 4

Critical Pre-Treatment Assessment

Before initiating PRP, you must:

• Assess for macular edema presence - If clinically significant macular edema exists, treat with focal photocoagulation and/or anti-VEGF prior to or concomitant with PRP 1
• Discuss specific side effects: peripheral visual field loss, potential worsening of macular edema, night vision impairment 1
• Obtain informed consent documenting risks of vision loss 1
• Fluorescein angiography is NOT routinely needed for effective PRP application 1

Special Population Considerations

Type 2 Diabetes:

• Earlier PRP is particularly beneficial - treating at severe NPDR or early PDR reduces risk of severe vision loss by 50% (2.5% versus 5%) compared to deferring until high-risk PDR 1

Type 1 Diabetes:

• Timing depends on follow-up reliability and fellow eye status 1

Pregnancy, Impending Cataract Surgery:

• These conditions increase progression risk and may warrant earlier PRP 1
• Anti-VEGF use in pregnancy is FDA Category C and should only be used if potential benefit outweighs fetal risk 1

Post-Treatment Monitoring and Rescue Therapy

Indications for Additional Treatment:

• Failure of neovascularization to regress 1
• Increasing neovascularization of retina or iris 1
• New vitreous hemorrhage 1
• New areas of neovascularization 1

Surgical Escalation:

Pars plana vitrectomy is indicated for: vitreous opacities interfering with vision or treatment, severe fibrovascular proliferation, or traction retinal detachment threatening or involving the macula 1

Common Pitfalls to Avoid

• Do not use partial or limited PRP - only full PRP following ETDRS protocol is proven effective 1
• Do not choose anti-VEGF for patients with questionable follow-up - their outcomes will be inferior to PRP 1
• Do not delay PRP when high-risk PDR is present - even if macular edema exists, treat both concomitantly rather than deferring PRP 1
• Do not assume modern lasers eliminate the need for adequate burn coverage - adjusting PASCAL settings may be necessary to maintain neovascularization regression 5