Can a patient reliably distinguish retinal arteritis from retinal phlebitis clinically?

Clinical Distinction Between Retinal Arteritis and Retinal Phlebitis

No, patients cannot reliably distinguish retinal arteritis from retinal phlebitis clinically—this requires ophthalmologic examination with specific fundoscopic findings and ancillary imaging, as the distinction has critical implications for immediate management including stroke prevention and vision-threatening complications. 1

Key Diagnostic Features That Distinguish Arteritis from Phlebitis

Retinal Arteritis - Critical Findings

Arterial involvement presents with boxcar segmentation (slow, segmented blood flow in arterioles), which is pathognomonic for arterial occlusive disease. 1 Additional arterial-specific findings include:

• Retinal vascular "boxcarring" - segmented blood flow visible on examination 2
• Cotton wool spots indicating acute ischemia of nerve fiber layer 2, 1
• Cherry-red spot at macula in central retinal artery occlusion 3
• Visible retinal emboli in embolic arterial disease 3
• Arterial sheathing and discontinuity of small and large retinal arteries 4
• No vascular leakage on fluorescein angiography in pure occlusive disease (collateral vessels don't leak) 2

Retinal Phlebitis - Distinguishing Characteristics

Venous involvement demonstrates perivenular sheathing, venous dilation and tortuosity, and extensive intraretinal hemorrhages along the distribution of affected veins. 2 Phlebitis-specific findings include:

• Venous sheathing or cuffing - white inflammatory infiltrate around veins 5
• Venous dilation and tortuosity - prominent in branch or central retinal vein occlusion 2
• Extensive flame-shaped hemorrhages following venous distribution 2
• Late vascular leakage on fluorescein angiography from inflamed venous walls 2
• Bilateral involvement more common in inflammatory phlebitis 5

Critical Etiologic Considerations by Age

Patients Over 50 Years

Giant Cell Arteritis (GCA) is the most common non-embolic cause of retinal arteritis in patients over 50 and represents an ophthalmologic emergency requiring immediate high-dose corticosteroids. 1, 3, 6

• Screen immediately for GCA symptoms: headache, scalp tenderness, jaw claudication, polymyalgia rheumatica, diplopia 3
• Check ESR and CRP immediately and start corticosteroids if clinical suspicion is high 1
• GCA causes simultaneous ischemia of inner retina, outer retina, and optic disc due to proximal ocular artery inflammation 3, 6

Embolic Arterial Disease (Any Age)

Embolic retinal artery occlusion presents with visible emboli, unilateral presentation, and no vascular sheathing. 3 Risk factors include:

• Carotid artery disease, atrial fibrillation, cardiac valve disease 3
• Smoking, hypertension, diabetes, hyperlipidemia 3
• Requires immediate stroke center referral within 24 hours - represents stroke equivalent with 3-6% stroke risk in first 1-4 weeks 1, 3

Diagnostic Algorithm Using Ancillary Testing

Fluorescein Angiography - The Gold Standard

Fluorescein angiography definitively distinguishes arteritis from phlebitis by documenting arterial filling times, vascular leakage patterns, and areas of nonperfusion. 1

Arteritis pattern on FA:

• Delayed arterial filling times indicating arterial occlusion 2, 3
• Areas of capillary nonperfusion without late leakage 2
• No dye leakage from collateral vessels in later frames 2

Phlebitis pattern on FA:

• Late vascular leakage from inflamed venous walls 2
• Venous staining and tortuosity 2
• Macular edema with petalloid leakage 2

Optical Coherence Tomography (OCT)

OCT identifies paracentral acute middle maculopathy (PAMM) which suggests arterial ischemia of the deep capillary plexus. 1, 3

• Acute arteritis: thickening and increased inner retinal reflectivity, PAMM 2, 3
• Chronic arteritis: inner retinal thinning 2, 3
• Phlebitis: macular edema, intraretinal cysts, subretinal fluid 2

Indocyanine Green Angiography

ICG angiography is particularly useful for visualizing choroidal circulation in suspected GCA, enabling deeper imaging than fluorescein. 2, 3

Critical Pitfalls to Avoid

Never Delay GCA Workup

In patients over 50 with arteritis, never delay GCA evaluation—check ESR/CRP immediately and start corticosteroids if clinical suspicion is high, even before temporal artery biopsy. 1 Delaying treatment risks irreversible vision loss in the fellow eye. 3, 6

Arteritis Requires Immediate Stroke Evaluation

All acute retinal artery occlusions require immediate stroke center referral within 24 hours for diffusion-weighted MRI and cardiovascular evaluation, regardless of suspected etiology. 2, 1, 3 The stroke risk is highest in the first 7 days and remains elevated for 30 days. 3

Don't Confuse Focal Phlebitis with Arteritis

Focal retinal phlebitis can produce macular edema and ultimately branch retinal vein occlusion at sites away from arteriovenous crossings. 7 This represents a distinct inflammatory entity affecting venules, not arterial disease. 7

Systemic Workup Depends on Clinical Context

In isolated retinal vasculitis without systemic symptoms, extensive laboratory testing yields false-positives in 20.8% of cases without identifying underlying disease. 8 However, when review of systems suggests systemic disease, targeted evaluation is warranted. 8

For phlebitis, always evaluate for: systemic hypertension (48% attributable risk), hyperlipidemia (20% attributable risk), diabetes (5% attributable risk). 2

Immediate Management Priorities

The distinction between arteritis and phlebitis determines immediate life-threatening versus vision-threatening management:

• Arteritis: Immediate stroke center referral, GCA evaluation if age >50, cardiovascular workup 2, 1, 3
• Phlebitis: Anti-VEGF therapy for macular edema, monitor for neovascularization, manage systemic vascular risk factors 2