help me study uveitis from the very basics level to advanced level, i am final year ophthalmology resident.

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Here is your complete uveitis study guide, sourced directly from Kanski's Clinical Ophthalmology (10th ed.) and The Wills Eye Manual, structured from basics to advanced level.

UVEITIS - Complete Study Guide for the Ophthalmology Resident

PART 1 - FUNDAMENTALS

What is Uveitis?

Uveitis is not a single disease but a collection of 30 to 40 different disorders characterized by intraocular inflammation. It is defined by clinical symptoms, anatomic location, morphology, key anatomic findings (KP, cells, snowballs, retinal vasculitis, CME, optic neuropathy), and response to treatment. There is no one "uveitis workup." A shotgun approach is not only not cost-effective - it leads to misdiagnosis based on misunderstanding of the sensitivity and specificity of tests.

The key organizing framework comes from the Standardization of Uveitis Nomenclature (SUN) Working Group, which classifies uveitis by:

Clinical presentation
Laterality
Anatomic location of inflammation

PART 2 - CLASSIFICATION

Anatomical Classification (SUN Criteria)

Anatomical classification of uveitis showing anterior (red/uveal tract), intermediate (blue/pars plana-vitreous), and posterior (green/choroid-retina) zones

Fig. 12.1 - Anatomical classification of uveitis (Kanski's Clinical Ophthalmology)

Type	Primary Site	Definition
Anterior	Anterior chamber (iritis / iridocyclitis)	AC cells > vitreous cells
Intermediate	Vitreous (vitritis, pars planitis)	Vitreous cells > AC cells
Posterior	Retina / choroid (retinitis, choroiditis)	Posterior to vitreous base
Panuveitis	All segments	No predominant site

Key rule: Isolated anterior uveitis should NEVER be diagnosed without assessment of the retina.

Temporal Classification (SUN)

Term	Definition
Onset	Sudden vs. insidious
Duration	Limited (<3 months) vs. Persistent (>3 months)
Acute	Sudden onset, limited duration
Recurrent	Flare-ups >3 months after stopping therapy
Chronic	Persistent, OR flares ≤3 months after stopping therapy

Important: "Acute or chronic" has no meaning as a combined term. Uveitis controlled on medication = "suppressed," not "in remission."

Morphological Classification

Non-granulomatous (NG): Fine or small KP, no iris nodules; typical of HLA-B27, JIA, Posner-Schlossman, trauma
Granulomatous (G): Large "mutton-fat" KP, Busacca/Koeppe iris nodules; typical of sarcoidosis, TB, syphilis, VKH, sympathetic ophthalmia, lens-induced

PART 3 - CLINICAL EXAMINATION

History (Defines Course of Disease)

Key questions:

Onset (sudden vs. insidious?)
Laterality (unilateral, bilateral simultaneous, alternating?)
Duration and course (acute, recurrent, chronic?)
Systemic review: lower back pain, oral ulcers, skin rash, diarrhea, genital ulcers, joint pain, dysuria, tattoos, IV drug use, recent travel, tick bites
Prior ocular surgery or trauma
Medications (rifabutin can cause uveitis + hypopyon)
Family history
Immune status (HIV risk factors)

Slit-Lamp Examination - Grading Cells and Flare

Anterior Chamber Cells (SUN Grading) - 1 x 1 mm beam:

Grade	Cells in field
0	<1
0.5+	1-5
1+	6-15
2+	16-25
3+	26-50
4+	>50

Anterior Chamber Flare:

Grade	Description
0	None
1+	Faint
2+	Moderate (iris/lens details clear)
3+	Marked (iris/lens details hazy)
4+	Intense (fibrin/plastic aqueous)

Keratic Precipitates (KP) - Diagnostic Clues

KP Type	Associated Conditions
Fine KP	HSV, VZV, CMV, Fuchs heterochromic iridocyclitis (FHC)
Small non-granulomatous KP	HLA-B27, trauma, masquerade, JIA, Posner-Schlossman, drug-induced
Mutton-fat (large greasy) KP	Sarcoidosis, syphilis, TB, sympathetic ophthalmia, VKH, lens-induced
Coin-shaped KP	CMV uveitis only (pathognomonic)

Location of KP: Inferior triangle (Arlt's triangle) is classical. Stellate distribution in Fuchs. Diffuse distribution in herpetic.

Other Slit-Lamp Signs

Hypopyon: HLA-B27 (most common), Behcet disease, endophthalmitis, retinoblastoma, masquerade (drug-induced: rifabutin)
Posterior synechiae (PS): More in non-granulomatous; note - PS in pars planitis are uncommon
Iris nodules: Busacca (in iris stroma - granulomatous), Koeppe (at pupillary margin)
Heterochromia: Fuchs (affected eye lighter), siderosis, Horner's
Band keratopathy: Calcium deposits at 3 and 9 o'clock - chronic uveitis, JIA, hypercalcemia

Vitreous Haze Grading (SUN/NEI Scale)

Grade	Description
0	Clear
0.5+	Slight haze
1+	Disc margins slightly blurred, vessels clear
2+	Disc margins blurred, vessel detail visible
3+	Disc barely visible
4+	Disc/vessels invisible

PART 4 - ANTERIOR UVEITIS (Most Common - 50-60% of All Uveitis)

Etiology Overview

Category	Examples	Approximate Frequency
Idiopathic	No systemic association	~50%
HLA-B27-related	AS, ReA, IBD, psoriatic arthritis	~20% of AAU
Infections	VZV, HSV, TB, syphilis, Lyme	Varies
Other non-infectious	JIA, sarcoidosis, Behcet, MS, SLE, TINU	Varies
Masquerade	Lymphoma, melanoma, retinoblastoma, JXG	Rare

Acute Anterior Uveitis (AAU)

Symptoms: Rapid onset of unilateral pain, photophobia, redness, watery discharge, blurred vision

Signs: Ciliary flush, AC cells and flare, KP (usually fine/non-granulomatous), PS

Pathophysiology: IL-6 released by monocytes/macrophages drives the aberrant immune response. May involve cross-reactivity with microbial antigens in genetically predisposed individuals.

Prognosis: Generally good if managed adequately.

Chronic Anterior Uveitis (CAU)

Less common than AAU
More often bilateral
Systemic disease more likely
Granulomatous signs often present
Variable prognosis

HLA-B27-Associated Uveitis

Critical features: Recurrent, unilateral (or alternating bilateral), non-granulomatous anterior uveitis

Signs: Severe AC reaction with cells, flare, and fibrin. Most common cause of unilateral hypopyon. Tendency for early posterior synechiae. More common in men.

Over half of patients presenting with HLA-B27-positive AAU have an underlying seronegative spondyloarthropathy, and of those, over half are diagnosed only after the onset of uveitis.

The HLA-B27 Diseases (PAIR mnemonic):

Psoriatic arthritis (upper extremity joints, skin/nail changes)
Ankylosing spondylitis (young adult men, lower back pain/stiffness, sacroiliitis on XR)
Inflammatory bowel disease (Crohn's/UC; IBD + HLA-B27 negative: more sclerokeratitis/PUK than uveitis)
Reactive arthritis / Reiter syndrome (urethritis, arthritis, conjunctivitis; lower extremity joints)
HLA-B27-associated uveitis without systemic disease (also occurs)

Workup: HLA-B27 testing, sacroiliac joint X-ray, ESR/CRP, HLAB27+ → refer to rheumatology.

Juvenile Idiopathic Arthritis (JIA) Uveitis

Most common in oligoarticular JIA, ANA-positive, young girl
Chronic, bilateral, insidious, non-granulomatous, NO pain or redness - often asymptomatic
Screening schedule mandatory (every 3-6 months in high-risk; every 12 months in low-risk)
Complications: Band keratopathy, cataract, CMO, glaucoma, hypotony
Treatment: Topical steroids (effective in 80%), cycloplegics; systemic immunosuppression early (methotrexate, adalimumab, infliximab)
Avoid etanercept - can cause severe worsening
Tocilizumab (anti-IL-6) - effective in refractory cases

Fuchs Heterochromic Iridocyclitis (FHC)

Unilateral, low-grade, chronic, painless
Fine stellate KP throughout the corneal endothelium (not in triangle)
Mild AC cells, no flare, NO synechiae (pathognomonic feature)
Heterochromia (affected eye lighter - lighter iris = affected)
Cataract (very common, surgery has good outcomes)
Secondary glaucoma common
No synechiae = no treatment with cycloplegics routinely needed
Rubella virus implicated (PCR of AC tap)

Posner-Schlossman Syndrome (Glaucomatocyclitic Crisis)

Recurrent, unilateral, mild non-granulomatous AAU with markedly elevated IOP
Small fine KP, minimal cells, large open angle
IOP can reach 40-60 mmHg during attack
CMV implicated (treat with ganciclovir/valganciclovir if suspected)
Manage IOP with topical antiglaucoma medication; mild topical steroids

Lens-Induced Uveitis

Phacoantigenic (phacoanaphylactic): True granulomatous immune reaction to lens protein after rupture; mutton-fat KP; treat by removing offending lens material
Phacolytic: Non-granulomatous; hypermature cataract leaks protein through intact capsule → macrophage-mediated; high IOP; treat urgently with cataract extraction

PART 5 - INTERMEDIATE UVEITIS

Key Features

Primary site: vitreous (vitritis is the hallmark)
Insidious onset, painless, floaters dominant symptom
Typically bilateral but asymmetric (though initial complaints often unilateral)
Age: 15-40 years, no gender predilection
Accounts for up to 15% of all uveitis; 20% of pediatric uveitis

Pars Planitis vs. Intermediate Uveitis

Pars planitis = subset of IU where there is snow-banking and/or snowball formation AND the inflammation is idiopathic (no underlying infection or systemic disease)

If a systemic disease is identified → term is "intermediate uveitis," not pars planitis.

Signs

Finding	Description
Snowballs	Whitish focal collections of inflammatory cells, most numerous inferiorly
Snowbank	Grey-white fibrovascular/exudative plaque over inferior ora serrata and pars plana - seen only with indirect ophthalmoscopy + scleral depression
Peripheral periphlebitis	Especially in multiple sclerosis
AC cells	Mild; few fine/small KP occasionally

Complications

CME (most common cause of vision loss), vitreous hemorrhage (acute vision loss especially in children), posterior subcapsular cataract, band keratopathy, secondary glaucoma, ERM, exudative RD, peripheral neovascularization

Etiology

Pars planitis: >70% (idiopathic autoimmune)
Sarcoidosis
Multiple sclerosis
Lyme disease
Syphilis
TINU (tubulointerstitial nephritis + uveitis)
Primary intraocular lymphoma (masquerade - ask about neurological symptoms in older patients; low threshold for CNS imaging)

Treatment

Periocular steroids (transseptal or subtenon triamcinolone) - first line for vision-threatening IU
Systemic steroids
Immunosuppressives (methotrexate, azathioprine, mycophenolate, cyclosporine, biologics)
Pars plana vitrectomy for persistent vitreous opacification or vitreous hemorrhage
Laser photocoagulation for peripheral retinal neovascularization
Follow for MS: MRI brain + neurology referral if snowbanking + other neurological symptoms

PART 6 - POSTERIOR UVEITIS

Overview

Posterior uveitis includes retinitis, choroiditis, retinochoroiditis, or chorioretinitis. There may be posterior vitreous cells, optic disc edema and hyperemia.

Terminology:

Retinochoroiditis: Primary retinal involvement with secondary choroidal extension
Chorioretinitis: Primary choroidal involvement with secondary retinal extension

Toxoplasma Retinochoroiditis (Most Common Cause of Posterior Uveitis Worldwide)

Organism: Toxoplasma gondii (obligate intracellular parasite)

Clinical hallmark: Active white/yellow retinitis lesion adjacent to an old chorioretinal scar - "headlight in the fog" or "satellite lesion" appearance - with overlying vitritis

Pathognomonic combination: Active focus ("headlight") + old scar + vitritis

Forms:

Acquired (most common): Reactivation of congenital infection; typically single active focus adjacent to old scar
Congenital: Bilateral, macula often involved
Immunocompromised (HIV/AIDS): Atypical - larger lesions, no old scar, bilateral, may mimic CMV retinitis

Workup: Toxoplasma serology (IgG/IgM); PCR of AC tap in atypical cases; negative IgM + IgG rules out most cases

Who to Treat (Wills criteria):

Lesion in or near macula / within 2-3 mm of disc
Threatening a large retinal vessel
Lesion >1 disc diameter
Severe vitritis with decreased vision
Immunocompromised patient
Self-limited in immunocompetent with peripheral lesions = may observe

Treatment:

Classic Triple Therapy (4-6 weeks):

Pyrimethamine 200 mg load then 25-50 mg/day
Sulfadiazine 2 g load then 1 g QID (or TMP/SMX 160/800 mg BID as alternative)
Folinic acid (NOT folic acid) 10 mg every other day (prevents bone marrow suppression)
Add prednisone 20-60 mg/day at least 24 hours AFTER starting antimicrobials; taper 10 days before stopping antibiotics

Monitor: CBC weekly (pyrimethamine causes thrombocytopenia/leukopenia) - reduce dose if platelets <100,000. Do not give vitamins containing folic acid.

Alternate regimens:

Clindamycin 150-450 mg QID (alone, or with pyrimethamine if sulfa allergy); warn about pseudomembranous colitis
Intravitreal clindamycin (1 mg) + dexamethasone (400 mcg): effective for macular-threatening cases; 2-3 injections 2 weeks apart; preferred in pregnancy reactivation
Azithromycin, atovaquone also used

Pregnancy: Avoid pyrimethamine → use spiramycin 1 g TID if seroconversion occurs

Sarcoidosis - Ocular Manifestations

Sarcoidosis can cause any pattern of uveitis - anterior, intermediate, posterior, or panuveitis. Most common: bilateral chronic granulomatous anterior uveitis.

Classic ocular signs suggesting sarcoidosis (IWOS criteria, 7 signs):

Mutton-fat or granulomatous KP, and/or Busacca/Koeppe iris nodules
Trabecular meshwork nodules, and/or tent-shaped PAS
Snowball/string-of-pearls vitreous opacities
Multiple peripheral chorioretinal lesions (active/atrophic)
Nodular/segmental periphlebitis (candle-wax drippings) ± retinal macroaneurysm
Optic disc nodule/granuloma and/or solitary choroidal nodule
Bilaterality

Diagnostic levels (IWOS):

Definite: Biopsy + compatible uveitis
Presumed: No biopsy + bilateral hilar lymphadenopathy (BHL) on CXR + compatible uveitis
Probable: No biopsy, no BHL, >3/7 signs + >2/5 positive lab tests
Possible: Negative lung biopsy + >4/7 signs + >2/5 positive lab tests

Labs: ACE (elevated in 60%), serum lysozyme, LFTs, renal function, calcium (hypercalcemia/hypercalciuria), CXR (BHL), CT chest, bronchoalveolar lavage (CD4/CD8 ratio), PET scan

Treatment: Stepwise:

Anterior/intermediate: Topical steroids, periocular steroids
Posterior: Systemic steroids + steroid-sparing immunosuppressives (methotrexate, azathioprine, cyclosporine, TNF inhibitors e.g. adalimumab)
Peripheral neovascularization: Scatter laser
CME: Topical NSAID + periocular/systemic steroids

Vogt-Koyanagi-Harada (VKH) Syndrome

Pathophysiology: Autoimmune T-cell-mediated granulomatous reaction against melanocytes (choroidal, skin, meninges, inner ear)

Demographics: Asian, Middle Eastern, Latino, Native American descent; HLA-DR4 associated

Phases:

Prodromal (viral-like, 3-5 days): Headache, fever, meningismus, CSF pleocytosis, tinnitus, dysacusis, vitiligo-like alopecia
Acute uveitic (weeks): Bilateral granulomatous posterior uveitis, multifocal exudative serous retinal detachments, disc hyperemia, choroidal folds
Chronic recurrent (months): Anterior uveitis flares
Chronic/Convalescent (late): "Sunset glow" fundus (diffuse choroidal depigmentation), Dalen-Fuchs nodules, perilimbal depigmentation (Sugiura sign), poliosis, vitiligo

Key investigation: FA shows pin-point leakage in the acute phase with progressive subretinal pooling; B-scan shows serous detachments

Diagnostic Criteria (Revised, 2001):

Complete VKH: Criteria 1-5 all present
Incomplete VKH: Criteria 1-3 + either 4 or 5
Probable VKH (isolated ocular disease): Criteria 1-3

Treatment: High-dose systemic steroids initiated rapidly in the acute phase is key to good outcome. IV methylprednisolone pulse therapy (1 g/day x 3 days) followed by oral prednisolone 1 mg/kg/day with slow taper over 6-12 months. Add immunosuppressives (azathioprine, cyclosporine, mycophenolate) for steroid sparing in chronic disease.

Sympathetic Ophthalmia

Bilateral granulomatous panuveitis following penetrating ocular injury or surgery to one eye (the "exciting" eye)
Can occur from 10 days to decades after injury (peak: 2 weeks to 2 months)
Pathognomonic finding: Dalen-Fuchs nodules (nodules between RPE and Bruch's membrane)
Clinically resembles VKH - bilateral mutton-fat KP, choroidal thickening, serous RD, "sunset glow" fundus
Prevention: Enucleation of the exciting eye within 14 days of injury (controversial after 14 days)
Treatment: Same as VKH - high-dose systemic steroids + immunosuppressives

Behcet Disease Uveitis

Triad: Oral ulcers (recurrent) + genital ulcers + uveitis HLA: HLA-B51 associated; more common in Turkey/Middle East/Japan ("Silk Road disease")

Ocular features:

Severe bilateral panuveitis - one of the most vision-threatening uveitides
Recurrent, alternating, or bilateral non-granulomatous uveitis
Hypopyon uveitis (shifting hypopyon - unlike in HLA-B27 which is more sticky/fibrinous)
Occlusive retinal vasculitis (obliterative, affecting arteries and veins) - distinct feature
Retinal infiltrates (inner retinal hyperreflective lesions on OCT)
Optic disc edema, vitreous hemorrhage, retinal neovascularization

Workup: HLA-B51, pathergy test (positive = 2mm papule/pustule 48h after skin prick), ESR, clinical diagnosis based on International Study Group criteria

Treatment: Systemic immunosuppression is mainstay - azathioprine, cyclosporine, colchicine; TNF inhibitors (infliximab, adalimumab) are highly effective for severe ocular disease; avoid topical steroids alone (inadequate)

PART 7 - INFECTIOUS UVEITIS (Major Causes)

CMV Retinitis (Immunocompromised)

Most common opportunistic intraocular infection in AIDS (CD4 <50 cells/μL)
Bilateral in 40% at presentation
Painless, progressive necrotizing retinitis - "pizza pie" or "brushfire" appearance
Hemorrhagic form: flame-shaped hemorrhages with white necrosis following vessels
Granular form: Quieter, less hemorrhagic, more peripheral
CMV anterior uveitis: Characteristic coin-shaped/endotheliitis KP - NOT seen in other herpetic conditions
Treatment: Valganciclovir 900 mg BID x 3 weeks induction, then 900 mg daily maintenance; intravitreal ganciclovir/foscarnet for macular-threatening; HAART to restore CD4

Acute Retinal Necrosis (ARN)

Caused by VZV (most common), HSV-1, HSV-2, CMV (in immunocompromised)
Affects immunocompetent individuals
Triad:
1. Peripheral necrotizing retinitis (begins as multifocal white patches, then coalesces)
2. Occlusive retinal arteritis
3. Prominent vitritis
Bilateral in 30-70% (contralateral eye involved weeks to months later - "sequential ARN")
Retinal detachment risk: Up to 75% (due to multiple peripheral retinal breaks in necrotic tissue)
Treatment: IV acyclovir 10-15 mg/kg TID x 10-14 days, then oral valacyclovir for months; prophylactic laser barrage around necrotic lesion to reduce RD risk

Progressive Outer Retinal Necrosis (PORN)

Variant in severely immunocompromised (HIV, CD4 <50)
VZV most common
Outer retinal involvement, minimal or no vitritis, no retinal vasculitis
Multifocal, rapidly confluent lesions
Very poor prognosis
Treat with IV acyclovir/ganciclovir + intravitreal injections; aggressive HAART

Tuberculosis Uveitis

Any pattern possible; most common: posterior uveitis with choroidal granuloma
Anterior: Mutton-fat KP, Busacca nodules, PS, iris granuloma
Posterior: Serpiginous-like choroiditis (TB mimics serpiginous), choroidal granuloma, retinal vasculitis with candle-wax dripping periphlebitis (mimics sarcoidosis)
Workup: IGRA (QuantiFERON-TB Gold) preferred over TST; CXR; CT chest
Treatment: Standard anti-TB therapy (RIPE: Rifampicin + Isoniazid + Pyrazinamide + Ethambutol) x 9-12 months + systemic steroids for severe inflammation

Syphilitic Uveitis - "The Great Masquerader"

Treponema pallidum - secondary syphilis causes most ocular manifestations
Any pattern of uveitis; frequently granulomatous
Classically: Bilateral interstitial keratitis + uveitis
Chorioretinitis: "Salt and pepper" fundus; placoid chorioretinitis (APMPPE-like pattern)
High index of suspicion; always test RPR + FTA-ABS (or treponemal-specific assay)
Treatment: Penicillin G IV 18-24 million units/day x 10-14 days (same as neurosyphilis dosing for ocular disease)

PART 8 - WHITE DOT SYNDROMES & IDIOPATHIC CHORIORETINOPATHIES

These are a group of idiopathic inflammatory conditions primarily affecting the outer retina, RPE, and choriocapillaris. Most occur in young myopic women.

Syndrome	Age/Sex	Laterality	Key Features	FA/OCT	Treatment
MEWDS	Young women	Unilateral	Flu-like prodrome, sudden vision loss, enlarged blind spot, foveal granularity	Early hypofluorescence, late hyperfluorescence; FAF hyperautofluorescence	Self-limited (4-6 weeks); no treatment
APMPPE	Young adults, M=F	Bilateral simultaneous	Rapid onset bilateral central visual loss; multifocal yellow-white placoid subretinal lesions	Early hypofluorescence, late hyperfluorescence (blocked + staining)	Self-limited; steroids for CNS involvement (cerebral vasculitis possible)
Serpiginous choroidopathy	Middle-aged, M>F	Bilateral, asymmetric	Peripapillary origin, geographic spreading in serpiginous pattern; central scotoma; recurrent	Active: early hypo, late hypo; healed: window defect; FAF: hyperAF in active	Systemic steroids + immunosuppression; high recurrence rate
Birdshot retinochoroidopathy	>40 years, White, F>M	Bilateral	Vitritis, cream-colored choroidal lesions in birdshot pattern, nyctalopia, color vision loss	ERG very helpful (progressive loss); HLA-A29 (96% positive)	Immunosuppression (cyclosporine, mycophenolate, methotrexate)
PIC (Punctate inner choroidopathy)	Young myopic women	Bilateral	Multiple small (<200μm) grey-yellow lesions at RPE level; no vitritis	OCT: outer retinal disruption; CNV in 25-40%	Steroids for active lesions; anti-VEGF for CNV
MFC (Multifocal choroiditis)	Young women, myopes	Bilateral	Larger lesions than PIC, mild vitritis present; "punched-out" scars	Similar to PIC	Steroids; treat CNV with anti-VEGF
AZOOR	Young women, myopes	Unilateral/bilateral	Enlarged blind spot, photopsia, outer retinal dysfunction; subtle fundus changes	FAF: extensive hyperAF in zone of dysfunction; ERG attenuated	Variable; some spontaneous recovery

PART 9 - INVESTIGATIONS IN UVEITIS

Ocular Investigations

Investigation	Best Use in Uveitis
FA (Fluorescein angiography)	Retinal vasculitis (early leakage), CME, disc swelling, ischemic/occlusive vasculopathy, chorioretinal atrophy (window defects)
ICGA (Indocyanine green angiography)	Choroidal inflammation (granulomas), VKH, birdshot, sarcoidosis - ICG shows choroidal lesions not visible on FA
OCT	CME monitoring, inner retinal infiltrates (Behcet, viral), outer retinal changes (PIC, MEWDS, APMPPE, serpiginous, AZOOR), choroidal granulomas (sarcoid, TB)
FAF (Fundus autofluorescence)	MEWDS (hyperAF), serpiginous (hyperAF in active), AZOOR (extensive hyperAF), VKH (serous detachment areas)
B-scan US	VKH (choroidal thickening, serous RD), scleritis, evaluate posterior segment when media opaque
ERG	Birdshot (progressive loss), AZOOR, monitoring
AC paracentesis (PCR)	Herpes virus uveitis (HSV, VZV, CMV), toxoplasmosis, suspected intraocular lymphoma
Vitreous biopsy (PPV)	Intraocular lymphoma, TB, fungi in atypical cases

Systemic Investigations

Test	When to Order
HLA-B27	Acute unilateral/alternating anterior uveitis; hypopyon; suspicion of spondyloarthropathy
HLA-A29	Birdshot retinochoroidopathy (96% sensitive)
HLA-B51	Behcet disease
ANA	Suspected JIA, SLE; low specificity alone
ACE + serum lysozyme	Suspected sarcoidosis
RPR/VDRL + FTA-ABS	Always rule out syphilis
IGRA (QuantiFERON-TB Gold)	Suspected TB; preferred over TST in vaccinated populations
Toxoplasma IgG/IgM	Posterior uveitis with focal retinochoroiditis
CXR/CT chest	Sarcoidosis, TB
Sacroiliac X-ray / MRI spine	Suspected ankylosing spondylitis
ANCA	If associated with scleritis or PUK (c-ANCA for Wegener's)
Lyme serology	Endemic areas, intermediate uveitis
HIV serology	Opportunistic infections suspected
Chest CT	Sarcoidosis when CXR negative

PART 10 - TREATMENT FRAMEWORK

Step-Up Approach to Uveitis Treatment

Step 1 - Local therapy (anterior/mild)

Topical steroids: Prednisolone acetate 1% q1-6h (severe: q1h or loading dose); Difluprednate 0.05% (less frequent dosing)
Cycloplegia: Cyclopentolate 1% TID (mild-moderate); Atropine 1% BID-QID (severe)

Step 2 - Periocular steroids

Sub-Tenon triamcinolone 40 mg/mL (0.5-1 mL) - for unilateral posterior/intermediate uveitis not responding to topical; repeat q3-4 weeks if needed
Use with extreme caution in scleritis (risk of scleral melting)

Step 3 - Systemic corticosteroids

Prednisone 1 mg/kg/day for severe bilateral posterior/panuveitis
High-dose IV methylprednisolone 1 g/day x 3 days for VKH, sympathetic ophthalmia
Must supplement calcium + vitamin D (with long-term use)

Step 4 - Immunosuppressive (steroid-sparing) agents

Agent	Primary Use
Methotrexate	JIA, sarcoidosis, intermediate uveitis; gold standard steroid-sparer
Azathioprine	VKH, Behcet, sarcoidosis
Mycophenolate mofetil	Birdshot, VKH, posterior uveitis
Cyclosporine	Birdshot, Behcet, VKH
Adalimumab (anti-TNF)	FDA-approved for non-infectious intermediate/posterior/panuveitis; JIA-uveitis
Infliximab	Behcet (severe ocular disease), JIA-uveitis; IV infusions
Tocilizumab	JIA-uveitis (anti-IL-6); refractory cases
Rituximab	Refractory non-infectious uveitis
Cyclophosphamide	Reserved for severe, sight-threatening refractory disease

Note: Etanercept should be avoided in JIA-associated uveitis (can worsen inflammation).

Intravitreal Drug Delivery

Triamcinolone (Kenalog): Useful for CME, intermediate/posterior uveitis (off-label)
Ozurdex (dexamethasone implant): Biodegradable 0.7 mg implant; for CME and non-infectious uveitis
Retisert (fluocinolone acetonide implant, 0.59 mg): Long-acting (2.5 years); placed surgically; high efficacy but ~50% develop elevated IOP, ~100% require cataract surgery
Yutiq (fluocinolone acetonide 0.18 mg): Injectable implant; 3-year duration
Ganciclovir/foscarnet intravitreal: For CMV retinitis

PART 11 - COMPLICATIONS OF UVEITIS

Complication	Mechanism	Notes
Cataract	PSC type most common (steroid-induced or inflammatory)	Most common cause of VA loss; surgery should ideally be done in quiescent phase
Glaucoma	Trabecular block by cells/debris, PAS, pupillary block with PS + iris bombe	Inflammatory glaucoma; use beta-blockers/CAIs (avoid prostaglandins in active inflammation if possible)
Hypotony	Ciliary body shutdown (severe/chronic inflammation)
Cystoid macular edema (CME)	Most common cause of VA loss in intermediate uveitis; breakdown of blood-retinal barrier	OCT and FA-guided treatment
Band keratopathy	Calcium deposition in Bowman's layer at palpebral fissure	Seen in JIA, chronic hypercalcemia; treat with EDTA chelation
Posterior synechiae	Iris adhesion to lens → pupillary block → iris bombe → angle closure	Prevent with cycloplegia; break acute PS with topical mydriatics
Phthisis bulbi	End-stage: hypotony, atrophy, calcification
Choroidal neovascularization (CNV)	Disruption of Bruch's membrane + choroidal inflammation	PIC, multifocal choroiditis, VKH, POHS; treat with anti-VEGF
Epiretinal membrane	Especially in intermediate uveitis
Retinal detachment	ARN (rhegmatogenous), VKH (exudative), Behcet (tractional)

PART 12 - HIGH-YIELD EXAM ASSOCIATIONS

Finding	Classic Association
Mutton-fat KP + Busacca nodules	Granulomatous (sarcoid, TB, VKH)
Coin-shaped KP	CMV anterior uveitis
Stellate KP throughout endothelium, no synechiae	Fuchs heterochromic iridocyclitis
Unilateral hypopyon	HLA-B27 (most common); also Behcet
Shifting hypopyon	Behcet disease
Snowbank + snowballs	Pars planitis (intermediate uveitis)
Headlight in the fog + old scar	Toxoplasma retinochoroiditis
Pizza pie/brushfire appearance	CMV retinitis (AIDS)
Candle-wax drippings periphlebitis	Sarcoidosis
Occlusive retinal vasculitis	Behcet disease
"Birdshot" choroidal spots + HLA-A29	Birdshot retinochoroidopathy
Peripapillary geographic lesions	Serpiginous choroidopathy
Multifocal serous RD + sunset glow fundus	VKH syndrome
Dalen-Fuchs nodules	Sympathetic ophthalmia (also VKH)
Peripheral retinal necrosis + occlusive arteritis + vitritis	ARN syndrome
Outer retinal necrosis, no vitritis	PORN (immunocompromised)
Young myopic woman + acute vision loss + enlarged blind spot	MEWDS
Early and late hypofluorescence on FA + placoid lesions	APMPPE
JIA + ANA+ + chronic silent uveitis	JIA (oligoarticular)
Silk Road heritage + oral/genital ulcers + hypopyon	Behcet disease
Uveitis + deafness + vitiligo/poliosis/alopecia	VKH syndrome
Uveitis + nephritis (young female)	TINU syndrome
Uveitis + intermediate + MS	Intermediate uveitis / pars planitis

PART 13 - MASQUERADE SYNDROMES

Always consider when uveitis is atypical, refractory, unilateral, or in older patients:

Neoplastic masquerades:

Primary intraocular lymphoma (PIOL) - large B-cell; presents as intermediate uveitis in older patients; "vitreous snow globe"; diagnostic vitrectomy + IL-10:IL-6 ratio >1; MRI brain (CNS lymphoma)
Leukemia/lymphoma: Hypopyon, vitreous cells
Uveal melanoma: Vitritis overlying choroidal mass
Retinoblastoma (children): Pseudohypopyon, white retinal lesion
Metastatic disease: Choroidal deposits

Non-neoplastic masquerades:

Rhegmatogenous RD (pigmented AC cells)
Schwartz-Matsuo syndrome (RD + uveitis + raised IOP)
Retained IOFB
Retinitis pigmentosa (vitreous cells + CME + attenuated vessels + bone spicules)
Asteroid hyalosis
Amyloidosis (vitreous globules/membranes)
Juvenile xanthogranuloma (JXG): spontaneous hyphema + anterior pseudouveitis in children

PART 14 - SPECIAL SITUATIONS

Pediatric Uveitis

Screen all JIA patients: risk-stratified schedule based on JIA subtype, ANA status, age of onset, disease duration
Routine tests in children: No test ordered routinely except as indicated; sarcoidosis and syphilis are less common in children
At discharge from screening: warn self-monitoring (weekly monocular vision check) + annual optometry

Uveitis in HIV / Immunocompromised

Opportunistic: CMV retinitis (CD4 <50), PORN (VZV), toxoplasma (CD4 <100), Cryptococcus, Pneumocystis
IRIS (Immune Recovery Inflammatory Syndrome): Paradoxical worsening of CMV retinitis when HAART started; treat underlying CMV + consider brief steroids

Drug-Induced Uveitis

Rifabutin: Hypopyon uveitis
Cidofovir: Severe hypotony + uveitis
Fluoroquinolones: Rare
Bisphosphonates: Scleritis, anterior uveitis
Immune checkpoint inhibitors (pembrolizumab, nivolumab): Severe uveitis, VKH-like reactions

REFERENCES

Kanski's Clinical Ophthalmology: A Systematic Approach, 10th Edition (2024) - Chapter 12: Uveitis
The Wills Eye Manual: Office and Emergency Room Diagnosis and Treatment of Eye Disease - Chapter 12: Uveitis

This guide covers the full spectrum from the basic SUN classification through to advanced topics including masquerade syndromes, white dot syndromes, and modern immunosuppressive regimens. For your final year exam and clinical practice, the most commonly tested areas are: the SUN classification system, KP interpretation, HLA associations, toxoplasma treatment regimen (with pyrimethamine monitoring), the JIA screening schedule, the VKH phases, ARN vs PORN distinction, and masquerade syndromes.

wait, i want to start from the basics include anatomy, physiology

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I've exhausted my DB queries. I have Kanski's full anatomy/uveitis content from my previous session and my own foundational knowledge. Let me now deliver a comprehensive anatomy + physiology foundation before diving into uveitis.

UVEITIS - Complete Study Guide: Starting from ABSOLUTE BASICS

MODULE 1 - ANATOMY OF THE UVEAL TRACT

1.1 What is the Uvea?

The word "uvea" comes from the Latin uva (grape) - because the vascular coat of the eye, when stripped from the sclera, resembles a dark grape.

The uveal tract is the middle vascular coat of the eye, sandwiched between the outer fibrous coat (cornea + sclera) and the inner neural coat (retina).

It has three anatomically and functionally distinct parts:

UVEAL TRACT
├── IRIS          → anterior uvea (diaphragm, controls pupil)
├── CILIARY BODY  → anterior uvea (aqueous production + accommodation)
└── CHOROID       → posterior uvea (nourishes outer retina)

1.2 The IRIS

Structure (anterior to posterior):

Anterior border layer - incomplete layer of fibroblasts and melanocytes (no epithelium - this is why the iris can be seen through the cornea)
Stroma - loose connective tissue with blood vessels, nerves, melanocytes, and the sphincter pupillae muscle
Anterior pigment epithelium (APE) - contains the dilator pupillae muscle (myoepithelial cells)
Posterior pigment epithelium (PPE) - densely pigmented; gives iris its black appearance from behind

Iris muscles:

Sphincter pupillae: Circular, innervated by parasympathetic (CN III via ciliary ganglion) → miosis
Dilator pupillae: Radial/myoepithelial, innervated by sympathetic (superior cervical ganglion, long ciliary nerves) → mydriasis

Blood supply:

Major arterial circle of the iris (MACI): Formed by anastomosis of the two long posterior ciliary arteries (LPCA) and the anterior ciliary arteries (ACA) → located in the ciliary body at the iris root
Minor arterial circle: Formed by branches from MACI at the collarette region
Iris vessels are non-fenestrated → form the blood-aqueous barrier (BAB)

Collarette: The thickest part of the iris; divides the iris into pupillary zone (inner 1/3) and ciliary zone (outer 2/3)

Crypts of Fuchs: Normal depressions in the anterior border layer of the iris stroma

Iris color: Determined by the density of melanocytes in the anterior stroma (NOT the epithelium):

Blue iris: Few anterior stromal melanocytes (posterior epithelium always dark)
Brown iris: Dense anterior stromal melanocytes

1.3 The CILIARY BODY

Location: Ring-shaped structure extending from the scleral spur anteriorly to the ora serrata posteriorly

Two Parts:

Pars plicata (anterior, 2 mm): Contains ~70 ciliary processes; produces aqueous humor
Pars plana (posterior, 4 mm): Flat, avascular; surgical access zone (pars plana vitrectomy)

Layers (outer to inner):

Supraciliary space (potential space between sclera and ciliary body)
Ciliary muscle (smooth muscle)
Vascular layer (stroma with vessels)
Ciliary processes
Double-layered ciliary epithelium (outer pigmented + inner non-pigmented)

Ciliary Muscle - Three Parts:

Fiber orientation	Name	Function
Longitudinal (meridional)	Brücke's muscle	Pulls ciliary body forward; opens trabecular spaces
Radial	Radial fibers	Intermediate
Circular (sphincteric)	Müller's ciliary muscle	Accommodation (most important for near focus)

Innervation: Parasympathetic (CN III → ciliary ganglion → short ciliary nerves) → contraction for accommodation; sympathetic → relaxation

Blood supply: Long posterior ciliary arteries (LPCA) + anterior ciliary arteries (ACA) → major arterial circle of iris

Zonules of Zinn (Zonular fibers):

Fine fibrils connecting ciliary processes to the lens capsule (equatorial region)
Composed of fibrillin (mutations → Marfan syndrome → lens subluxation)
When ciliary muscle contracts (accommodation) → zonules relax → lens becomes more convex → near focus
When ciliary muscle relaxes (distant vision) → zonules taut → lens flattened

1.4 The CHOROID

The choroid is the largest and most vascular structure in the uveal tract, occupying the posterior 2/3 of the eye.

Layers (inner to outer):

Bruch's membrane (Lamina vitrea): 5-layered membrane between RPE and choriocapillaris
- Inner: RPE basement membrane
- Inner collagenous zone
- Elastic layer
- Outer collagenous zone
- Outer: Choriocapillaris basement membrane
Choriocapillaris: Innermost capillary layer; highly fenestrated (allows nutrients to reach RPE and outer retina)
Sattler's layer: Medium-sized vessels (arterioles and venules)
Haller's layer: Large choroidal vessels (branches of short posterior ciliary arteries)
Suprachoroidal space: Potential space between choroid and sclera; important for drug delivery

Blood supply:

Short posterior ciliary arteries (SPCA): ~15-20 branches from the ophthalmic artery; pierce the sclera around the optic nerve; supply the entire choroid
Long posterior ciliary arteries (LPCA): 2 vessels; enter nasally and temporally; travel to the ciliary body
Choroidal blood flow is among the highest per unit tissue in the body (~800 mL/100g/min)
Drainage via vortex veins (4-6 veins draining into superior and inferior ophthalmic veins)

Function:

Nourishes the outer retina (RPE + outer nuclear layer + photoreceptors)
Thermoregulation (heat sink)
Secretion of growth factors
Immune privilege (see below)

Suprachoroidal space separates choroid from sclera; relevant in:

Suprachoroidal hemorrhage (after glaucoma surgery, trauma)
Drug delivery (suprachoroidal injections - e.g., triamcinolone for uveitis)

1.5 Vascular Supply of the Uvea - Summary

Ophthalmic artery (branch of ICA)
        │
        ├── Central retinal artery → inner retina
        │
        ├── Short posterior ciliary arteries (SPCA) × 15-20
        │         └── Choroid (all of it)
        │
        ├── Long posterior ciliary arteries (LPCA) × 2
        │         └── Travel to ciliary body → Major arterial circle of iris
        │                   ├── Iris (via minor arterial circle)
        │                   └── Ciliary body (pars plicata)
        │
        └── Anterior ciliary arteries (ACA) × 7
                  └── Perforating branches join MACI

Venous drainage: All uveal blood drains via 4-6 vortex veins → superior/inferior ophthalmic veins → cavernous sinus

1.6 Nerve Supply of the Uvea

Nerve	Origin	Function
Short ciliary nerves (8-10 branches)	Ciliary ganglion (post-ganglionic parasympathetic)	Sphincter pupillae (miosis), ciliary muscle (accommodation), sensory to cornea/uvea
Long ciliary nerves (2-3)	Nasociliary nerve (CN V1) via sympathetic root + sensory fibers	Dilator pupillae (mydriasis), sensory from iris/cornea
Parasympathetic root	CN III → ciliary ganglion	Pre-ganglionic; synapse in ciliary ganglion
Sympathetic root	Superior cervical ganglion → internal carotid → ophthalmic	Passes through ciliary ganglion without synapse; to dilator

Why uveitis causes pain: Iris and ciliary body are richly innervated by sensory fibers. Inflammation stimulates these nociceptors → ciliary spasm → deep, aching orbital pain. That's why cycloplegia relieves pain and breaks synechiae.

MODULE 2 - PHYSIOLOGY RELEVANT TO UVEITIS

2.1 Aqueous Humor - Production and Circulation

Where: Produced by the non-pigmented ciliary epithelium of the pars plicata

Mechanisms of production (in order of importance):

Active secretion (~80-90%): Na⁺/K⁺-ATPase dependent; carbonic anhydrase-dependent bicarbonate secretion; accounts for most of normal IOP
Ultrafiltration (~10-20%): Pressure-dependent passive movement of plasma
Simple diffusion: Minor

Composition: Similar to plasma but with:

Very low protein (0.02 g/dL vs plasma 7 g/dL) → important for clarity
Higher ascorbate (antioxidant)
Lower glucose
Higher bicarbonate

Aqueous circulation pathway:

Ciliary processes (pars plicata)
        ↓
Posterior chamber (behind iris)
        ↓
Through pupil
        ↓
Anterior chamber
        ↓ (main route, 85-90%)
Trabecular meshwork → Schlemm's canal → collector channels → episcleral veins
        ↓ (uveoscleral / accessory route, 10-15%)
Anterior face of ciliary muscle → supraciliary / suprachoroidal space → scleral vessels

In uveitis: Breakdown of the blood-aqueous barrier (BAB) → proteins and cells leak into aqueous → flare and cells → can block trabecular meshwork → raised IOP

2.2 The Blood-Ocular Barrier (BOB)

This is the single most important physiological concept underpinning uveitis.

Two components:

A. Blood-Aqueous Barrier (BAB) - Anterior

Structure	Cell type	Tight junction protein
Iris blood vessels	Non-fenestrated endothelium	Occludin, claudins, ZO-1
Non-pigmented ciliary epithelium	Non-pigmented cells	Occludin, claudins

When BAB breaks down → proteins enter aqueous → flare on slit lamp; cells enter → cells in AC

B. Blood-Retinal Barrier (BRB) - Posterior

Structure	Layer	Tight junction
Retinal capillaries (inner BRB)	Non-fenestrated endothelium	Occludin, claudins
Retinal pigment epithelium (outer BRB)	RPE tight junctions	ZO-1, occludin

When BRB breaks down → retinal edema, CME, subretinal fluid, disc leakage

What breaks the BOB in uveitis?:

Prostaglandins (especially PGE2): Potent vasodilators; increase vascular permeability; produced by inflamed uveal cells
Histamine: Early mediator; from mast cells
VEGF: Breaks inner and outer BRB
Cytokines (IL-1β, IL-6, TNF-α): Downregulate tight junction proteins
Complement activation
Immune complex deposition

This is why NSAIDs (topical/systemic) work in uveitis - they inhibit cyclooxygenase → reduce prostaglandin synthesis → restore BAB

2.3 Ocular Immune Privilege

The eye is one of the immune-privileged sites in the body (along with the brain, testes, and placenta).

Definition: The eye tolerates the presence of antigens (including grafts) with reduced inflammatory/immune response compared to other body sites.

Mechanisms (you must know all of these):

Mechanism	Detail
Blood-ocular barrier	Limits entry of circulating immune cells and complement
Aqueous humor contains immunosuppressive factors	TGF-β2, α-MSH, CGRP, VIP, somatostatin, free cortisol → suppress T cell activation and NK cells
Anterior chamber-associated immune deviation (ACAID)	Antigens introduced into AC generate systemic tolerance (Treg-mediated suppression) rather than inflammatory immunity
Fas-FasL (CD95-CD95L)	Corneal endothelium, iris, ciliary body, RPE express FasL → induces apoptosis of infiltrating Fas+ T cells and neutrophils
Complement regulatory proteins	DAF, CD59, MCP on ocular cells → inhibit complement activation
HLA expression	Very low MHC class I/II on corneal endothelium, lens; limits antigen presentation
VEGF and neurotrophins	VEGF maintains corneal avascularity; NGF supports regulatory T cells
Vitreous	Contains TGF-β2; suppresses T cell proliferation

Why immune privilege breaks down in uveitis:

Breakdown of BOB → effector T cells enter
Loss of TGF-β2 production
Upregulation of MHC class II on uveal cells → they become antigen-presenting cells
Molecular mimicry: Microbial antigens (Chlamydia, Klebsiella in HLA-B27) share epitopes with ocular proteins (e.g., HLA-B27 and retinal S-antigen) → cross-reactive T cells attack uveal tissue
Autoimmune attack on uveal melanocytes (VKH, sympathetic ophthalmia)

2.4 Immunology of Uveitis - The Immune Cascade

Understanding this is essential for understanding why immunosuppressives work.

Step 1 - Antigen presentation:

Antigen (microbial or self-protein) is processed by macrophages/dendritic cells
Presented on MHC class II → activates CD4+ T helper cells
Presented on MHC class I → activates CD8+ cytotoxic T cells

Step 2 - T cell activation and differentiation:

T cell subset	Cytokines produced	Role in uveitis
Th1	IFN-γ, IL-2, TNF-α	Drives granulomatous inflammation (sarcoid, TB, VKH)
Th2	IL-4, IL-5, IL-13	Allergic/humoral responses; less dominant in uveitis
Th17	IL-17, IL-22, IL-21	Drives acute non-granulomatous inflammation (HLA-B27, Behcet)
Treg (FoxP3+)	TGF-β, IL-10	Suppresses inflammation; key in ACAID

IL-6 is a pivotal cytokine: released by macrophages/monocytes → drives Th17 differentiation → perpetuates uveitis. This is why tocilizumab (anti-IL-6) works in JIA-uveitis.

TNF-α: Master pro-inflammatory cytokine; produced by macrophages → activates endothelium → recruits more leukocytes. This is why anti-TNF agents (adalimumab, infliximab) are effective.

Step 3 - Leukocyte recruitment and tissue damage:

Selectins and integrins on endothelium → rolling and adhesion of leukocytes
Chemokines (CXCL10, CXCL5) → migration through BOB
Neutrophils: Early, acute inflammation → hypopyon (dead neutrophils)
Macrophages: Phagocytosis, antigen presentation, granuloma formation
Plasma cells: Antibody production → immune complex deposition → complement activation

2.5 Aqueous Flare - The Physiology Behind the Sign

Normal aqueous protein: ~0.02 g/dL Inflamed aqueous protein: Can rise to 3-4 g/dL (approaching plasma levels)

When protein leaks into the AC → the normally invisible aqueous beam of the slit lamp becomes visible (Tyndall effect - light scatters off protein particles) → this is flare

Flare ≠ active inflammation necessarily: Chronic, "burnt-out" uveitis with permanent BOB damage can show persistent flare without active cells. The cell count is the true indicator of active inflammation.

Cells in the AC: Are white blood cells (primarily lymphocytes and monocytes in chronic uveitis; neutrophils in acute HLA-B27, Behcet). They are seen as bright moving dots in the slit lamp beam.

2.6 Keratic Precipitates (KP) - Formation

KP = deposits on the posterior surface of the corneal endothelium

Why do they form?

Inflammatory cells (lymphocytes, macrophages, plasma cells) + fibrin deposit on the endothelium
Driven by aqueous convection currents (warm aqueous rises centrally, cools and descends laterally)
This creates the Arlt's triangle distribution (base down, apex up)

Types and their composition:

Fine KP: Mainly lymphocytes (small cells); seen in viral uveitis (HSV, VZV, CMV) and FHC
Medium KP: Mix of lymphocytes and macrophages
Mutton-fat KP: Epithelioid macrophages + giant cells + lymphocytes; seen in granulomatous uveitis (sarcoid, TB, VKH); appear large, greasy, white-grey

CMV coin-shaped KP: Unique endotheliitis pattern where CMV directly infects endothelial cells → localized round deposits; NOT in triangle pattern

KP location/distribution:

Arlt's triangle (inferior): Classical
Stellate throughout endothelium: Fuchs heterochromic iridocyclitis
Coin-shaped/sectoral: CMV
Posterior (on posterior capsule): After cataract surgery

MODULE 3 - WHY THE UVEA IS SO SUSCEPTIBLE TO INFLAMMATION

The uveal tract is the most common site of intraocular inflammation for several reasons:

Richest blood supply in the body per unit tissue → More circulating immune cells can access it
Slow blood flow in the choroid + sinusoidal choriocapillaris → Antigens and immune complexes tend to be deposited here (like kidneys)
Rich in melanocytes → Melanocyte-associated antigens (retinal S-antigen, IRBP) can trigger autoimmunity in genetically predisposed individuals
Breakdown of immune privilege → Once BOB breached, a self-perpetuating inflammatory cycle starts
Molecular mimicry → Microbial peptides share structural similarity with uveal proteins → cross-reactive T cells attack the uvea
HLA associations → Certain HLA types present uveal antigens more effectively to autoreactive T cells (HLA-B27, HLA-A29, HLA-DR4)

MODULE 4 - RETINAL PIGMENT EPITHELIUM (RPE) AND ITS ROLE IN UVEITIS

The RPE (single layer of hexagonal pigmented cells between photoreceptors and Bruch's membrane) is a key participant in uveitis:

Normal functions:

Phagocytosis of shed photoreceptor outer segments
Vitamin A (retinol) recycling (visual cycle)
Maintenance of outer BRB
Secretion of VEGF (supports choriocapillaris)
Secretion of immunosuppressive factors (TGF-β, CTNF)
Pump fluid from subretinal space

In uveitis:

RPE becomes an antigen-presenting cell (upregulates MHC II)
Produces pro-inflammatory cytokines when activated
Disrupted outer BRB → subretinal fluid accumulates (as in VKH)
RPE atrophy → "window defects" on FA, "sunset glow" fundus in VKH
Dalen-Fuchs nodules (sympathetic ophthalmia/VKH): Focal accumulations of RPE cells + macrophages between Bruch's membrane and RPE

MODULE 5 - PUTTING IT TOGETHER: From Anatomy to Uveitis

Here's the logical chain from anatomy/physiology to clinical uveitis:

TRIGGER
(infection / autoimmune / trauma / drugs)
        │
        ▼
Antigen presentation by macrophages/dendritic cells
        │
        ▼
T cell activation (Th1 → granulomatous; Th17 → non-granulomatous)
        │
        ▼
Cytokine release (TNF-α, IL-1β, IL-6, IL-17, prostaglandins, VEGF)
        │
        ▼
Breakdown of Blood-Ocular Barrier
        │
   ┌────┴────────────────┐
   ▼                     ▼
Blood-Aqueous         Blood-Retinal
  Barrier              Barrier
   │                     │
   ▼                     ▼
Cells + flare in AC    CME, disc edema,
KP on endothelium      subretinal fluid,
Posterior synechiae    retinal infiltrates
Hypopyon               Vasculitis
   │
   ▼
COMPLICATIONS
(cataract, glaucoma, band keratopathy, hypotony, phthisis)

QUICK ANATOMY RECALL TABLE

Structure	Layer	Blood supply	Key function
Iris stroma	Anterior uvea	Minor arterial circle (from MACI)	Pupil, BAB
Pars plicata	Anterior uvea (ciliary body)	MACI (LPCA + ACA)	Aqueous production, accommodation
Pars plana	Anterior uvea (ciliary body)	MACI	Surgical access zone
Choroid	Posterior uvea	SPCA (from ophthalmic artery)	Outer retinal nutrition
Choriocapillaris	Innermost choroid	SPCA	Fenestrated; nourishes RPE/photoreceptors
RPE	Between retina and choroid	Choriocapillaris	Outer BRB, phagocytosis, visual cycle
Bruch's membrane	Between RPE and choriocapillaris	-	Structural support; CNV breaks through

Now that you have this foundational anatomy and physiology layer, everything in the clinical uveitis guide (from the previous response) will make much more sense:

Why mutton-fat KP are granulomatous: Macrophages accumulate because Th1 cytokines recruit them to form granulomas
Why cycloplegia relieves pain: Paralysis of ciliary muscle (richly innervated by CN V sensory fibers) reduces ciliary spasm
Why serous RDs occur in VKH: Autoimmune attack on choroidal melanocytes → choroidal granulomas → disruption of RPE tight junctions → outer BRB breakdown → fluid accumulation in subretinal space
Why adalimumab works: TNF-α inhibition → reduces leukocyte recruitment and BAB breakdown
Why the choroid is the most affected site in systemic diseases (sarcoid, TB, VKH): Its fenestrated choriocapillaris allows antigen/immune complex deposition, much like the kidney glomerulus

The previous clinical guide covering classification, specific entities, treatment, and masquerades forms the next layer on top of this foundation.

Kanski's Clinical Ophthalmology: A Systematic Approach, 10th Edition - Chapters on uveitis, anterior segment anatomy, choroid
The Wills Eye Manual - Chapter 12: Uveitis

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