How to differentiate between retinal arteritis and retinal phlebitis?

Distinguishing Retinal Arteritis from Retinal Phlebitis

Retinal arteritis and phlebitis are differentiated primarily by fluorescein angiography findings: arteritis shows delayed arterial filling, arterial wall staining, and segmental arterial occlusion, while phlebitis demonstrates venous wall staining, perivenular hemorrhages, and irregular venous caliber with dilated segments. 1, 2

Clinical Presentation Patterns

Arteritis Features

• Arterial involvement strongly suggests infectious etiology (57.9% in infectious uveitis vs 11.2% in non-infectious), making this the most critical distinguishing feature 2
• Focal or elongated segmental arterial sheathing with vessel discontinuity 3
• Cotton-wool spots indicating focal ischemia 4, 3
• Sclerotic arterial segments with narrowed caliber 3
• Kyrieleis plaques (white deposits along vessels) 3
• More commonly associated with severe vision loss 3, 2

Phlebitis Features

• Venous involvement is more common in both infectious and non-infectious uveitis but less specific for etiology 2
• Perivenular hemorrhages as a hallmark finding 3
• Irregular venous caliber with alternating dilated and sclerotic segments 3
• Venous sheathing (white lines along vessel walls) 2
• Often bilateral presentation, particularly in isolated retinal vasculitis 5
• May progress to branch retinal vein occlusion at the site of inflammation 6

Fluorescein Angiography: The Definitive Test

FA is the confirmatory diagnostic test that definitively distinguishes arteritis from phlebitis 1, 7

Arteritis on FA

• Delayed retinal arterial filling in early phases 4, 3
• Arterial wall staining and leakage 2
• Retinal capillary nonperfusion in arterial distribution 4, 3
• Segmental arterial occlusion patterns 2

Phlebitis on FA

• Venous wall staining and leakage 2
• Delayed venous drainage 2
• Venous occlusion patterns (typically at non-arteriovenous crossing sites in isolated phlebitis) 6
• Macular edema from venous leakage 6, 5

Critical Etiologic Distinction

The presence of arteritis (especially inflammatory artery sheathing at 33.7% vs 0% and artery occlusion at 22.1% vs 3.7%) strongly indicates infectious uveitis and mandates urgent systemic workup 2

When Arteritis Predominates

• Pursue infectious workup aggressively: tuberculosis, syphilis, acute retinal necrosis, cytomegalovirus, fungal, bacterial 2
• Consider giant cell arteritis if patient >50 years with systemic symptoms (headache, jaw claudication, temporal tenderness) 4
• Obtain ESR and CRP urgently if GCA suspected 1

When Phlebitis Predominates

• Consider non-infectious causes: sarcoidosis, Behçet's disease, systemic lupus erythematosus 2, 5
• Evaluate for isolated retinal vasculitis (5.7% of all retinal vasculitis cases) 5
• Still exclude infectious causes, as phlebitis occurs in both groups 2

Ancillary Diagnostic Tools

OCT Findings

• Detects macular edema (common in phlebitis) 1, 8
• Shows inner retinal thickening and hyperreflectivity in acute arterial occlusion 4
• Quantifies structural damage but doesn't distinguish vessel type involved 1

Fundus Photography

• Documents vascular sheathing patterns and caliber changes 1, 7
• Tracks hemorrhage distribution (perivenular in phlebitis) 3
• Monitors disease progression over time 1

Common Diagnostic Pitfalls

• Vitreous cells may obscure retinal vascular details in arteritis, requiring high index of suspicion 3
• Peripheral vasculitis may be asymptomatic initially, requiring dilated peripheral examination 9
• Both arteritis and phlebitis can coexist in the same patient, particularly in infectious uveitis 2
• Isolated focal phlebitis can mimic branch retinal vein occlusion but occurs away from arteriovenous crossings 6
• FA carries rare but serious risks (1 in 200,000 mortality) and requires informed consent and emergency protocols 1, 7

Immediate Management Implications

Arteritis requires more urgent intervention due to higher risk of severe vision loss and potential systemic disease 3, 2

• Arteritis with suspected GCA: immediate high-dose corticosteroids before biopsy 4
• Infectious arteritis: targeted antimicrobial therapy based on etiology 2
• Phlebitis: systemic corticosteroids (82% of cases) with consideration for additional immunosuppression (27% of cases) 5
• Both conditions may require intravitreal therapy, panretinal photocoagulation, or vitrectomy depending on severity 5