How are etiologies of retinal vasculitides classified based on the vessels affected predominantly?

Classification of Retinal Vasculitides Based on Vessels Affected

Retinal vasculitides are classified into three primary categories based on the predominant vessel type involved: arterial vasculitis (retinal arteritis), venous vasculitis (retinal phlebitis), and capillary vasculitis. 1, 2, 3

Primary Classification Framework

The classification system for retinal vasculitis is fundamentally organized by vessel caliber and location:

Venous Vasculitis (Retinal Phlebitis)

• Predominantly affects retinal veins and presents with venous sheathing, perivascular infiltrates, and inflammatory changes along the vessel wall 1
• May be associated with branch retinal vein occlusion, though this should be distinguished from primary thrombotic/embolic vein occlusions which lack true inflammatory vessel wall changes 4
• Venous involvement is more commonly seen in noninfectious etiologies and typically shows less ischemia than arterial disease 5

Arterial Vasculitis (Retinal Arteritis)

• Involves retinal arterioles with arterial sheathing, narrowing, and occlusion 2, 3
• More frequently associated with infectious etiologies and tends to exhibit more severe ischemic changes 6
• Arterial occlusion patterns suggest infectious causes, particularly when combined with retinal or choroidal involvement 6

Capillary Vasculitis

• Affects the retinal capillary network and is predominantly associated with noninfectious retinal vasculitis 6
• Presents with capillary leakage, microaneurysms, and diffuse retinal edema 3
• More difficult to visualize on clinical examination but well-demonstrated on fluorescein angiography 3

Secondary Classification Considerations

Occlusive vs. Non-Occlusive Pattern

• Retinal vasculitis can be further subclassified as occlusive (with vessel closure and ischemia) or non-occlusive (with inflammation but preserved perfusion) 5
• Occlusive disease carries higher risk for complications including neovascularization, vitreous hemorrhage, and neovascular glaucoma 5
• Infectious vasculitis tends toward occlusive patterns with ischemic areas, while noninfectious disease more commonly shows non-occlusive capillary involvement 6

Location-Based Classification

• Peripheral retinal vasculitis affects vessels in the retinal periphery 2
• Posterior pole vasculitis involves vessels near the optic disc and macula 2
• Ultra-widefield imaging has improved detection of peripheral vascular involvement that may be missed on standard examination 5

Important Distinction: Choriovasculitis

• Choriovasculitis is a separate entity involving inflammation of the choroidal circulation posterior to the retina, distinct from retinal vasculitis 4
• Seen in conditions like Vogt-Koyanagi-Harada disease and white dot syndromes 4
• Requires indocyanine green angiography (ICGA) for optimal detection, as fluorescein angiography primarily images retinal vessels 4

Clinical Pitfalls

• Do not confuse retinal vein occlusion with venous vasculitis: retinal vein occlusions are primarily thrombotic/embolic processes lacking the inflammatory vessel wall changes characteristic of true vasculitis 4
• Infectious vasculitis typically shows arterial or venous sheathing/occlusion with ischemic areas, while noninfectious disease more commonly presents with capillary vasculitis 6
• The distinction between vessel types affected has direct therapeutic implications, as infectious and noninfectious etiologies require fundamentally different treatment approaches 7