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Retinal Vasculitis: Basic to Advanced

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1. DEFINITION

Key point from Firestein & Kelley: Retinal vasculitis is diagnosed clinically and angiographically - not histologically - because retinal biopsy carries prohibitive morbidity. The term is somewhat imprecise because it does not always indicate true vessel wall destruction.

• Firestein & Kelley's Textbook of Rheumatology, p. 4462

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2. EPIDEMIOLOGY

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3. CLASSIFICATION

By vessel affected:

• Arteritis - arteries involved; typically severe, ischemic, sight-threatening
• Phlebitis / Periphlebitis - veins involved; more common, predominantly inflammatory
• Capillaritis - capillaries; macular edema dominant
• Panvasculitis - both arteries and veins (classic in Behçet disease, SLE)

By etiology:

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4. PATHOPHYSIOLOGY & IMMUNOLOGY

TRIGGER ANTIGEN
(microbial, autoantigen, immune complex)
           ↓
  TLR signaling + Complement activation
           ↓
  CD4+ Th1 → IFN-γ
  CD4+ Th17 → IL-17        ← Innate/Adaptive immune bridge
  TNF-α, IL-6, IL-10
           ↓
  Breakdown of BLOOD-RETINAL BARRIER (BRB)
           ↓
  Leukocyte adhesion (ICAM-1, VCAM-1)
  Neutrophil/Monocyte transmigration
           ↓
  PERIVASCULAR CUFFING (histology hallmark)
           ↓
  Vascular occlusion → Ischemia → VEGF upregulation
           ↓
  Neovascularization → Vitreous hemorrhage / TRD

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5. CLINICAL FEATURES

Symptoms (what the patient complains of):

Signs (what you see on examination):

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6. CHARACTERISTIC FUNDUS PATTERNS BY ETIOLOGY

Eales Disease

• Classic "young Indian male" peripheral periphlebitis
• Peripheral venous disease → ischemia → NVE → recurrent vitreous hemorrhage
• Diagnosis of exclusion; associated with hypersensitivity to tubercular protein
• Staging: Stage I = Periphlebitis | Stage II = Ischemia | Stage III = NVE | Stage IV = Regression

Behçet Disease

• Occlusive vasculitis affecting both arteries AND veins - the most severe form
• Explosive, recurrent attacks with dense vitritis, retinal hemorrhage, disc swelling
• Associated with oral/genital aphthae, skin pathergy; HLA-B51 positive
• Cumulative ischemic damage over repeated episodes → optic atrophy
• Without treatment: 74% of eyes have VA worse than 20/200 within 5 years - Firestein & Kelley, p. 364

Sarcoidosis

• "Candle-wax drippings" (taches de bougie) - perivenous nodular exudates, the pathognomonic sign
• Also: vitreous "string of pearls," choroidal granulomas, disc granuloma (Lauber's spot), sea fan NVE
• Granulomatous periphlebitis; often bilateral
• Look for bilateral hilar lymphadenopathy, elevated ACE/serum lysozyme

TB-associated Vasculitis

• Peripheral perivenous sheathing ± choroidal tubercles or tuberculoma
• Can mimic Eales disease exactly - many "Eales" cases show TB serology evidence
• Confirm with Mantoux/IGRA, chest CT, aqueous PCR where feasible
• QuantiFERON-TB Gold: specificity 97%, sensitivity 78% (preferred in BCG-vaccinated)

MS-Associated Vasculitis

• Peripheral retinal periphlebitis (venous sheathing) in a subset of MS patients
• Overlaps with pars planitis; inferior peripheral "snowbanking" and vitreous "snowballs"
• Sheathing may be subclinical, detectable only on FFA

IRVAN Syndrome (Idiopathic Retinal Vasculitis, Aneurysms, Neuroretinitis)

• Rare; affects healthy young women - Kanski's, p. 516
• Multiple fusiform arteriolar aneurysms clustered near major bifurcations and disc
• Neuroretinitis with macular star exudate
• Progressive peripheral capillary non-perfusion → NVE
• Steroids have little effect on retinal ischemia; responds to infliximab

Frosted Branch Angiitis (FBA)

• Severe diffuse perivascular sheathing of BOTH arteries and veins - the "frosted branch" appearance
• Primary (idiopathic, children/young adults, often self-limited) or secondary (CMV, HSV, sarcoidosis, lymphoma)
• Treatment: systemic corticosteroids + treat the underlying cause

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7. IMAGING - FFA, ICGA, OCT, OCT-A

Fundus Fluorescein Angiography (FFA) - the Gold Standard Investigation

Key teaching point: FFA is mandatory because fundoscopy underestimates activity. Widefield FFA (Optos/Heidelberg 200° field) detects 30-50% more peripheral non-perfusion than 7-field photography.

ICG Angiography (ICGA)

• Detects choroidal involvement - hypofluorescent spots (granulomas in sarcoid, Behçet)
• Better visualization of choriocapillaris ischemia and deep vessel detail
• In Birdshot chorioretinopathy: multiple hypofluorescent spots beyond visible fundus lesions

OCT Findings

OCT-Angiography (OCT-A)

• Maps the superficial and deep capillary plexus without dye injection
• Detects capillary dropout / foveal avascular zone (FAZ) enlargement
• Identifies subclinical NVE flow
• Limitation: cannot detect leakage (only structural flow mapping)

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8. SYSTEMIC WORKUP ALGORITHM

Tier 1 - ALL Patients

• CBC, ESR, CRP
• Serum ACE (sarcoidosis)
• VDRL/TPHA (syphilis)
• Chest X-ray / CT chest
• Mantoux / IGRA (TB)
• Toxoplasma IgG/IgM
• RA factor, ANA, dsDNA (SLE)
• ANCA (systemic vasculitis)
• HLA-B51 (Behçet, especially in endemic populations)

Tier 2 - Selected Cases

• MRI brain (MS, CNS sarcoidosis)
• Fluorescein / ICGA angiography
• Anterior chamber tap for PCR/cytology (viral, lymphoma)
• PET-CT (occult malignancy, systemic sarcoid)
• Vitreous biopsy (masquerade syndromes)

Clinical Pearl #1: Always exclude infection before starting immunosuppression. TB and syphilis are the great mimickers.

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9. DIFFERENTIAL DIAGNOSIS

Infectious Mimics

• CMV retinitis: perivascular "frosting" + hemorrhagic necrosis; immunocompromised patients
• ARN (Acute Retinal Necrosis, HSV/VZV): peripheral full-thickness necrosis with occlusive arteritis
• Syphilitic uveitis: multifocal, FTA-ABS positive; the "great imitator"
• Toxoplasmosis: focal retinochoroiditis + adjacent vasculitis - "headlight in fog" appearance

Non-Inflammatory Vascular Masquerades

• CRVO/BRVO: disc edema, flame hemorrhages, venous dilation (no leukocytic cuffs on FFA)
• Diabetic retinopathy: NVE/NVD + microaneurysms (no inflammatory cells)
• Hypertensive retinopathy: AV nipping, hard exudates, copper/silver wiring
• Radiation retinopathy: history of orbital/ocular radiation

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10. TREATMENT PROTOCOLS

Step 1 - Treat the Underlying Cause (if infectious)

For TB: Never start steroids before ATT in confirmed TB. In probable ocular TB, simultaneous start is acceptable. Expect a paradoxical reaction (10-40% worsen initially) - add oral prednisolone 0.5 mg/kg/day after 4 weeks of ATT.

Step 2 - Control Inflammation (Non-infectious)

Step 3 - Steroid-Sparing Immunosuppression

Step 4 - Biologic Agents

Step 5 - Laser and Surgery

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11. DISEASE-SPECIFIC PROTOCOLS

Behçet Disease

• Posterior uveitis/vasculitis → Azathioprine + systemic corticosteroids (1st line)
• Severe/vision-threatening → Anti-TNF (infliximab or adalimumab)
• Acute attack → Systemic CS + cyclosporine 4-5 mg/kg/day
• Avoid cyclosporine monotherapy due to neurological toxicity risk

• Recurrent oral ulceration (mandatory) + 2 of: genital ulceration, ocular lesions (uveitis/vasculitis), skin lesions (erythema nodosum, pseudofolliculitis), positive pathergy test

Sarcoidosis

• Systemic and/or periocular corticosteroids first
• Steroid-sparing agents for chronic disease (methotrexate, mycophenolate)
• Always confirm with tissue biopsy when possible; chest CT for hilar adenopathy

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12. COMPLICATIONS & PROGNOSIS

Prognosis by Disease

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13. KEY CLINICAL PEARLS (Fellowship Level)

1. Always exclude infection before immunosuppression. TB and syphilis mimic every form of non-infectious vasculitis.
2. FFA is mandatory - fundoscopy consistently underestimates disease activity. Widefield FFA detects 30-50% more peripheral NPA.
3. CME is the leading cause of VA loss (40-60% of patients). OCT-guided therapy is the standard of care.
4. Behçet retinal vasculitis - anti-TNF biologics (infliximab/adalimumab) are disease-modifying. Start early, do not wait for conventional therapy failure.
5. Adalimumab is the only FDA-approved biologic for non-infectious uveitis (VISUAL I & II Trials, 2016).
6. PRP + anti-VEGF combination is superior to PRP alone for NVE in Eales - RCT evidence (2018).
7. OCT-A reveals subclinical capillary dropout and FAZ enlargement even in clinically quiet eyes - prognostically important.
8. TB paradoxical reaction: 10-40% worsen initially on ATT. Do not abandon treatment - add steroids after 4 weeks of ATT.
9. Cyclosporine monotherapy in Behçet is contraindicated due to neurotoxicity risk.
10. IGRA (QuantiFERON-TB Gold) is preferred over Mantoux in BCG-vaccinated populations (specificity 97%, sensitivity 78%).

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14. LATEST EVIDENCE (2026)

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Summary Mind Map

RETINAL VASCULITIS
│
├── DEFINITION: Inflammation of retinal vessels + intraocular inflammation
│     ± vascular occlusion
│
├── TYPES: Arteritis (severe/ischemic) | Phlebitis (common) | Capillaritis | Panvasculitis
│
├── PATHOPHYSIOLOGY
│     TLR → Th1/Th17 → TNF-α/IL-17/IFN-γ → BRB breakdown → cuffing → occlusion
│
├── ETIOLOGY MNEMONICS
│     BEST-BITE: Behçet, Eales, Sarcoid, TB | Syphilis, Infectious (CMV/ARN), TB, others
│
├── INVESTIGATION HIERARCHY
│     Fundoscopy → FFA (mandatory) → OCT/OCT-A → ICGA → Blood workup (Tier 1 & 2)
│
├── TREATMENT LADDER
│     Treat infection → Corticosteroids → Immunosuppressants → Biologics → Laser/Surgery
│
└── LEADING CAUSE OF VA LOSS: CME (40-60%) → OCT-guided prompt treatment

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Retinal Anatomy, Physiology & Applied Aspects to Vasculitis

A Complete Teaching Session - Basics to Advanced

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PART 1 - RETINAL ANATOMY

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1.1 What Is the Retina?

• Active fluid transport by the RPE (out of the subretinal space)
• Interdigitation of RPE microvilli with photoreceptor outer segments
• Intraocular pressure

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1.2 The Ten Layers of the Retina

Memory trick: I Never Give Idiots Any Of Our Precious Retinas (ILM, NFL, GCL, IPL, INL, OPL, ONL, OLM, Photoreceptors, RPE) - from vitreous to choroid.

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1.3 Key Cell Types and Their Roles

Photoreceptors - The Transducers

Bipolar Cells

• Midget bipolar: 1:1 connection with foveal cones → high acuity
• Diffuse bipolar: converge multiple rods → high sensitivity (but less acuity)
• ON-center bipolar: depolarize to light
• OFF-center bipolar: hyperpolarize to light

Horizontal Cells

• Lateral inhibition between adjacent photoreceptors
• Responsible for contrast enhancement at edges

Amacrine Cells

• ~30 subtypes; modulate ganglion cell responses
• Play a role in motion detection and directional selectivity

Ganglion Cells (RGCs)

• The only output neuron of the retina
• Their axons form the optic nerve
• Magnocellular (M-cells): motion and low contrast
• Parvocellular (P-cells): fine detail and colour

Müller Cells - The Retinal Glia

• Span the ENTIRE retina from ILM to OLM
• Act as structural scaffolding, metabolic support, potassium buffering (spatial K⁺ buffering)
• Release VEGF under hypoxia → drive neovascularization
• In vasculitis: Müller cell dysfunction → macular edema amplification

Retinal Pigment Epithelium (RPE)

• A single layer of hexagonal cells
• 10 critical functions:
  1. Absorbs stray light (melanin granules)
  2. Phagocytoses shed photoreceptor outer segment discs (~30,000 discs/cell/day)
  3. Re-isomerizes all-trans retinal → 11-cis retinal (visual cycle)
  4. Maintains ionic environment of subretinal space
  5. Active fluid transport (keeps subretinal space dry)
  6. Forms the outer blood-retinal barrier (tight junctions)
  7. Secretes trophic factors for photoreceptors
  8. Secretes VEGF toward choroid (maintains choriocapillaris)
  9. Secretes anti-VEGF PEDF apically
  10. Immune modulation: secretes immunosuppressive factors (TGF-β, CXCL16, IL-10) - critical for immune privilege

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1.4 The Fovea and Macula

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PART 2 - RETINAL BLOOD SUPPLY (VASCULAR ANATOMY)

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2.1 The Dual Blood Supply - The Most Important Concept in Retinal Disease

                    RETINA
         ┌──────────────────────────┐
         │  INNER 2/3 of retina     │  ← RETINAL CIRCULATION
         │  (NFL to INL)            │     (Central retinal artery branches)
         │──────────────────────────│
         │  OUTER 1/3 of retina     │  ← CHOROIDAL CIRCULATION
         │  (ONL, photoreceptors,   │     (Short posterior ciliary arteries
         │  RPE)                    │      → choriocapillaris)
         └──────────────────────────┘

• Retinal artery occlusion kills inner retina but spares photoreceptors (initially)
• Choroidal ischemia kills photoreceptors and RPE but spares inner retina
• Retinal vasculitis primarily affects the inner retinal circulation

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2.2 The Retinal Circulation in Detail

• CRA is an end artery - no collateral anastomoses with other retinal arteries
• Cilioretinal artery (present in ~20% of eyes) arises from posterior ciliary circulation → spares a strip of retina in CRA occlusion
• The retinal circulation lacks autonomic innervation (unlike choroidal) - autoregulation is entirely myogenic and metabolic
• A-V ratio normally 2:3 (artery:vein diameter) - reversal suggests hypertension or vascular disease

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2.3 The Retinal Capillaries - The Site of Vasculitis

• Superficial/inner plexus: in the ganglion cell layer
• Deep/outer plexus: in the inner nuclear layer
• Both connect at the macula to form a complex ring

1. Endothelial cells - single layer; linked by tight junctions = the inner blood-retinal barrier
2. Basement membrane - lies beneath endothelial cells
3. Pericytes - external to endothelium; enclosed by outer basal lamina; have pseudopodal processes enveloping the capillary

• Around arterioles (arteriolar capillary-free zone)
• At the fovea (FAZ - foveal avascular zone, ~0.35 mm)

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2.4 The Choroidal Circulation

• Supplied by short and long posterior ciliary arteries (from the ophthalmic artery)
• The choriocapillaris is a fenestrated capillary bed (unlike retinal capillaries)
• Blood flow: ~70 ml/min/100g tissue - the highest perfusion rate in the body
• Functions as the metabolic supply to the outer retina (no autoregulation - entirely pressure-dependent)
• Fenestrated walls allow fluorescein leakage into the extravascular space → blocked by RPE tight junctions = outer BRB

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PART 3 - THE BLOOD-RETINAL BARRIER (BRB)

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3.1 Inner BRB (iBRB)

• Location: Tight junctions (zonula occludentes) between retinal capillary endothelial cells
• Also known as: the retinal vascular barrier
• Prevents passage of both bound and free fluorescein, proteins, and inflammatory cells
• Pericytes and basement membrane play only a minor supportive role in barrier function - the endothelial tight junctions are the key element - Kanski's, p. 2508
• Integrity maintained by: VEGF antagonism (PEDF), angiopoietin-1 from pericytes, occludin/claudin tight junction proteins

• Inflammatory cytokines: VEGF, TNF-α, IL-1β, IL-6 → downregulate occludin, claudin-5
• Leukocyte transmigration → mechanical disruption
• Complement activation → membrane attack complex (MAC)
• Pericyte loss (early event in diabetic retinopathy and vasculitis)

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3.2 Outer BRB (oBRB)

• Location: Tight junctions between RPE cells (zonula occludentes)
• The choriocapillaris is fenestrated (leaky) → fluorescein freely leaks into the extravascular space
• RPE cells physically block this fluorescein from entering the subretinal space
• Disruption of oBRB → subretinal fluid accumulation, RPE detachments, exudative retinal detachment

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PART 4 - RETINAL PHYSIOLOGY

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4.1 Visual Transduction (Phototransduction)

• cGMP levels are HIGH
• cGMP-gated Na⁺ channels are OPEN → Na⁺ flows in continuously (the "dark current")
• Rod membrane potential: -40 mV (relatively depolarized)
• Glutamate is continuously released at the synaptic terminal
• This continuously INHIBITS ON-bipolar cells

LIGHT
  ↓
Photon absorbed by rhodopsin (outer segment disc)
  ↓
11-cis retinal → all-trans retinal (photoactivation)
  ↓
Activated rhodopsin (metarhodopsin II)
  ↓
Activates TRANSDUCIN (G-protein, Gα)
  ↓
Transducin activates cGMP PHOSPHODIESTERASE (PDE)
  ↓
cGMP hydrolyzed to 5'-GMP → cGMP levels FALL
  ↓
cGMP-gated Na⁺ channels CLOSE
  ↓
Dark current stops; K⁺ continues to exit
  ↓
HYPERPOLARIZATION (membrane potential → -70 to -80 mV)
  ↓
Glutamate release STOPS
  ↓
ON-bipolar cells DEPOLARIZE → ganglion cells fire

• Activated rhodopsin phosphorylated by rhodopsin kinase → arrestin binding → inactivation
• Transducin-GTP → Transducin-GDP (intrinsic GTPase activity)
• PDE deactivated
• Guanylyl cyclase restores cGMP
• Na⁺/Ca²⁺-K⁺ exchanger restores Ca²⁺ levels
• All-trans retinal transported to RPE → re-isomerized to 11-cis retinal (the visual cycle, requiring vitamin A)

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4.2 Retinal Oxygen Metabolism

• Oxygen consumption: ~5 mL O₂/100g/min (among the highest of any tissue)
• The photoreceptor inner segments are packed with mitochondria to sustain the enormous ATP demand of the dark current (Na⁺/K⁺-ATPase)

Vitreous (PO₂ ~10 mmHg)
    ↑
Inner retina ← supplied by CRA branches (PO₂ ~30-40 mmHg at NFL)
    ↑
Outer retina ← almost no oxygen (PO₂ approaches 0 mmHg at ONL)
    ↑
Choriocapillaris (PO₂ ~60-70 mmHg) ← outer retina's sole oxygen source

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4.3 Retinal Autoregulation

1. Myogenic autoregulation (Bayliss effect): Smooth muscle in arterioles contracts when transmural pressure rises → maintains constant flow over an IOP/BP range of 30-80 mmHg ocular perfusion pressure
2. Metabolic autoregulation: Tissue hypoxia → local adenosine/NO release → vasodilation
3. Pericyte-mediated regulation: Pericytes contract/relax at the capillary level (the retinal-specific mechanism)

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PART 5 - OCULAR IMMUNE PRIVILEGE (The Foundation of Why Vasculitis Is Unique in the Eye)

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5.1 What Is Immune Privilege?

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5.2 How Immune Privilege Breaks Down in Retinal Vasculitis

TRIGGER (microbial antigen, autoantigen, immune complex)
           ↓
  Pattern recognition by TOLL-LIKE RECEPTORS (TLR2, TLR4, TLR9)
  on retinal endothelial cells and RPE
           ↓
  NF-κB activation
           ↓
  Upregulation of:
  - ICAM-1 (intercellular adhesion molecule-1)
  - VCAM-1 (vascular cell adhesion molecule-1)
  - P-selectin, E-selectin
  on retinal vessel endothelium
           ↓
  Leukocyte ROLLING, ADHESION, TRANSMIGRATION
  (leukostasis in retinal capillaries)
           ↓
  CD4+ T-cells: Th1 (IFN-γ) + Th17 (IL-17) infiltrate perivascular space
           ↓
  PERIVASCULAR CUFFING (white sheathing visible on fundoscopy)
           ↓
  Inflammatory cytokines (TNF-α, IL-6, VEGF) released:
  → Disrupt tight junction proteins (occludin, claudin-5)
  → BRB BREAKDOWN → CME (macular edema)
  → Endothelial apoptosis → vascular wall necrosis → OCCLUSION
           ↓
  ISCHEMIA → HIF-1α upregulation → VEGF surge
           ↓
  NEOVASCULARIZATION (NVE, NVD)
           ↓
  Vitreous hemorrhage, TRD, optic atrophy

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PART 6 - CLINICAL ANATOMY-PHYSIOLOGY CORRELATION

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6.1 Why Periphlebitis Is More Common Than Periarteritis

1. Venous blood flow is slower → longer leukocyte contact time with endothelium
2. Venous endothelium expresses higher baseline ICAM-1
3. Venous walls are thinner and less able to resist inflammatory cell infiltration
4. At arteriovenous crossings, artery and vein share a common adventitial sheath → arterial inflammation can spread to adjacent vein

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6.2 Why the FAZ Is Clinically Critical

• Capillary dropout advances toward the FAZ
• FAZ enlargement on OCT-A is the earliest sign of ischemic maculopathy
• FAZ >0.6 mm → high risk of irreversible central vision loss
• Even if clinical inflammation is controlled, enlarged FAZ predicts poor final VA

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6.3 Why CME Is the Leading Cause of VA Loss

1. The macular capillaries form a dense double-ring perifoveal network (inner and outer plexuses)
2. Tight junction disruption from inflammatory cytokines → leakage into Henle's fiber layer (OPL) and inner nuclear layer
3. Müller cells cannot adequately reabsorb fluid under sustained inflammatory stress
4. Fluid accumulates in petaloid cystic spaces → distorts photoreceptor-bipolar synapses at OPL
5. The photoreceptors themselves are pushed away from RPE → outer segment ischemia even without choroidal involvement

• Cystoid intraretinal fluid (IR fluid) in OPL and INL
• Petaloid pattern on cross-section
• Subretinal fluid if severe (oBRB secondary failure)
• Ellipsoid zone disruption in chronic CME = photoreceptor death = poor visual prognosis

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6.4 Why Cotton Wool Spots = Ischemia (Not Exudates)

• Arteriolar occlusion by vasculitic thrombus or fibrin plug
• Ischemia in capillary-free zone around arteriole (see anatomy above)
• Rapid axoplasmic transport depends on local ATP → halts within hours of ischemia
• Swollen axons appear white on fundoscopy
• Disappear in 4-6 weeks as the axons degenerate

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6.5 Why Neovascularization Occurs and Why It Destroys Vision

1. Ischemic retina → HIF-1α (hypoxia-inducible factor) → massive VEGF upregulation
2. VEGF acts on retinal endothelium → new vessel sprouting (NVE = neovascularization elsewhere, NVD = at disc)
3. New vessels are abnormal: no tight junctions → profuse leakage (explains late leakage on FFA)
4. New vessels grow into the vitreous space along posterior hyaloid face
5. Posterior vitreous detachment → fibrovascular frond traction → vitreous hemorrhage
6. Progressive fibrous proliferation → sheets over retina → tractional retinal detachment

• Destroys ischemic peripheral retina → eliminates VEGF source
• Remaining perfused retina receives better oxygen supply
• Neovascular regression occurs in ~80% (Eales Stage III-IV)

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6.6 Why Widefield FFA Detects More Disease

• Standard 7-field FFA covers ~60° of fundus
• Widefield (Optos/Heidelberg) covers 200° in one image
• Peripheral retina is where early periphlebitis and NPA begin in Eales, TB, sickle cell, MS
• The peripheral capillary bed is supplied by the most terminal arteriolar branches → first to fail in inflammatory occlusive disease
• 30-50% more non-perfusion area detected with widefield imaging → changes management decisions regarding PRP timing

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6.7 Anatomy of Arteriovenous Crossings and BRVO

• Arterial wall inflammation spreads to the vein through this shared sheath
• • Venous endothelial turbulence at the crossing
• • Hypercoagulable state from systemic inflammation → Branch retinal vein occlusion (BRVO)

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6.8 Why Optic Disc Hyperfluorescence Matters

• Capillaries derived from the posterior ciliary arteries (Zinn-Haller ring) + CRA branches
• A fenestrated capillary bed on the disc surface
• No BRB at the disc → fluorescein normally leaks slightly (disc staining normal late)

• Peripapillary capillary inflammation → early disc hyperfluorescence (not late leakage alone)
• Disc edema from axonal ischemia
• In Behçet: disc vasculitis with necrosis → very poor prognosis

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PART 7 - VISUAL PATHWAY ANATOMY (Connecting Retina to Brain)

Photoreceptors (retina)
    ↓ (via bipolar cells → ganglion cells)
Optic nerve (CN II) → optic chiasm
    ↓
Optic tract → Lateral Geniculate Nucleus (LGN)
    ↓
Optic radiations (Meyer's loop anteriorly, 
                  Baum's loop posteriorly)
    ↓
Primary Visual Cortex (V1) - striate cortex, occipital pole

• Optic neuritis in MS-related vasculitis = demyelination of optic nerve = RAPD
• Severe disc vasculitis (Behçet) = optic atrophy = permanent field defect
• Sectoral NPA from BRVO = corresponding scotoma mapped on visual field testing

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Summary: Anatomy-Physiology-Vasculitis Integration Table

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