Occular tb full details for md exam answer 15 marks

Reading File

Finding Sources

Searching PubMed

"ocular tuberculosis" diagnosis treatment

Finding Sources

Reading File

Finding Sources

Reading File

Finding Sources

Reading File

Loading Image

I now have comprehensive information. Let me compose the full MD exam answer:

Ocular Tuberculosis — Complete MD Exam Answer (15 Marks)

1. Introduction & Epidemiology

Tuberculosis (TB) is a chronic granulomatous infection caused by Mycobacterium tuberculosis (rarely M. bovis or atypical mycobacteria such as M. avium in immunocompromised patients). TB is primarily a pulmonary disease but spreads haematogenously to extrapulmonary sites — ocular involvement commonly occurs without clinically overt systemic disease, making it a great imitator. Immune deficiency (HIV, diabetes, malnutrition, immunosuppressive therapy) is a major risk factor.

2. Pathogenesis

Two mechanisms operate:

Mechanism	Description
Direct infection	Haematogenous seeding of uveal tissue (choroid most vascular) → granuloma formation with caseating necrosis
Hypersensitivity	Immune-mediated reaction to mycobacterial antigens — explains many anterior uveitis episodes, phlyctenulosis, serpiginoid choroiditis, and possibly Eales disease

3. Ocular Manifestations (Site-by-Site)

A. Eyelids

Lupus vulgaris — reddish-brown nodules; a form of cutaneous TB

B. Conjunctiva

Conjunctivitis — granulomatous, with associated preauricular lymphadenopathy (Parinaud oculoglandular syndrome)
Phlyctenulosis — hypersensitivity-mediated; small, nodular, limbal or corneal lesions with intense injection; classic in children

C. Cornea

Interstitial keratitis — stromal haze, vascularisation; less common than syphilis but well-documented
Marginal ulcers (hypersensitivity)

D. Sclera

Scleritis (anterior or posterior) — nodular or diffuse; can be necrotising

E. Anterior Uvea (Most Common Segment in TB Uveitis)

Usually granulomatous anterior uveitis
Mutton-fat keratic precipitates (KPs) on corneal endothelium
Iris nodules (Koeppe at pupil margin, Busacca in iris stroma)
Broad posterior synechiae (PS), peripheral anterior synechiae
Secondary glaucoma, complicated cataract

F. Vitreous

Viritis — very common; may be secondary to anterior, intermediate, or posterior primary foci
Snowballs, snowbanking
Macular complications: cystoid macular oedema (CMO), epiretinal membrane

G. Choroid (Most Characteristic Posterior Segment Lesion)

Choroidal granuloma (tubercle) — focal, elevated, dome-shaped yellowish lesion; unilateral or bilateral; solitary or multiple. A large abscess-like lesion = tuberculoma
Serpiginoid (multifocal serpiginous-like) choroiditis — multifocal lesions spreading centrifugally; tracking retinal vessels has reasonable specificity for TB; distinguished from true serpiginous choroiditis by distribution and response to ATT
Miliary choroidal tubercles — pathognomonic of miliary TB; multiple tiny bilateral choroidal lesions; vital sign on ophthalmoscopy in suspected miliary TB

H. Retina & Retinal Vasculitis

Retinal vasculitis, preferentially venous (periphlebitis/sheathing of retinal veins)
Retinal haemorrhages
Vascular occlusion → branch retinal artery/vein occlusion → extensive ischaemia
Pre-retinal and disc neovascularisation (NVI/NVE) → vitreous haemorrhage
Eales disease — recurrent vitreous haemorrhage in young males from idiopathic retinal periphlebitis; TB hypersensitivity is a leading aetiological hypothesis
Exudative retinal detachment

I. Optic Nerve

Optic neuritis / neuroretinitis — may be direct infiltration or para-infectious
Optic atrophy (late)

4. Fundus Images (Kanski's Clinical Ophthalmology)

Fig. A — Choroidal granuloma (Tubercle): Solitary dome-shaped yellowish elevated lesion in posterior pole.

Tuberculous choroiditis — Choroidal granuloma (A)

Fig. B — Active multifocal choroidal TB: Multiple pale-yellow lesions with arrow indicating confluent active foci; overlying exudate and disc oedema.

Tuberculous choroiditis — Active multifocal (B)

5. Diagnosis

Diagnosis of ocular TB is often clinical — based on clinical picture + evidence of TB exposure or latency + exclusion of other causes. A formal systemic assessment by an appropriate specialist is mandatory.

Systemic Investigations

Test	Details
Tuberculin skin test (Mantoux)	Positive ≥48h; false-negatives in anergy (HIV, malnutrition); false-positives with BCG
IGRA — Interferon-Gamma Release Assay (QuantiFERON-TB Gold)	~80% sensitivity in active disease; independent of BCG vaccination; preferred in BCG-vaccinated populations
T-SPOT.TB	Counts antimycobacterial effector T cells producing IFN-γ; can detect latent TB; sensitivity 81%, specificity 86%
Sputum — AFB smear + culture	Ziehl-Neelsen staining; Löwenstein-Jensen medium; PCR
Chest X-ray	Primary complex, Ghon's focus, apical fibronodular lesions, hilar lymphadenopathy
CT / PET-CT	Mediastinal nodes, pulmonary cavities, extrapulmonary TB
HIV status	Must be determined in all patients

Ocular Investigations

Test	Details
Aqueous/vitreous sampling	AFB smear + ZN stain; culture on Löwenstein-Jensen; PCR (highly specific, variable sensitivity — gold standard for ocular fluid)
Fundus fluorescein angiography (FFA)	Establishes choroidal activity; confirms preretinal NV; demonstrates ischaemia
Fundus autofluorescence (FAF)	Activity staging — lesions become progressively hypoautofluorescent with healing
OCT	Macular evaluation — CMO, subretinal fluid, ERM
B-scan ultrasonography	Posterior scleritis, choroidal thickening, retinal detachment

Diagnostic criteria (Gupta et al. / SUN Workshop): Probable ocular TB = compatible ocular lesion + positive IGRA/TST + evidence of systemic TB (radiological or biopsy) + no alternative diagnosis. Confirmed = direct demonstration of AFB or positive PCR/culture from ocular fluids.

6. Treatment

Anti-Tubercular Therapy (ATT)

Prolonged multi-drug therapy, prescribed and monitored by a specialist with experience in systemic TB management.

Standard regimen (WHO):

Intensive phase (2 months): Isoniazid (H) + Rifampicin (R) + Pyrazinamide (Z) + Ethambutol (E) — 2HRZE
Continuation phase (4–10 months): Isoniazid + Rifampicin — 4HR (extrapulmonary TB often treated for 9–12 months total)

Key drug ocular side effects:

Ethambutol → optic neuropathy (monitor visual acuity, colour vision, fields regularly)

Rifabutin (used in HIV co-infection in place of rifampicin) → anterior uveitis (often hypopyon)

Isoniazid → optic neuritis (rare); supplement pyridoxine (B6)

Role of Corticosteroids

Topical steroids: for anterior segment inflammation (cycloplegia also for posterior synechiae prevention)
Systemic steroids: used concomitantly with ATT to reduce inflammation-induced damage, particularly in early weeks when paradoxical worsening of fundal appearance may occur
Must NEVER be given without ATT cover
Especially indicated for: optic neuritis, extensive choroiditis, CMO, exudative RD, orbital TB

Additional Ocular Treatment

Indication	Treatment
Posterior synechiae	Cycloplegics (atropine) + topical steroids
Raised IOP / secondary glaucoma	IOP-lowering agents; trabeculectomy if refractory
Retinal neovascularisation	Laser photocoagulation to ischaemic retina
Vitreous haemorrhage	Observation → vitrectomy if non-clearing
Cataract	Phacoemulsification after inflammation controlled

Evidence Update

Treatment with ATT in patients with uveitis associated with latent TB halves the risk of uveitis recurrence and delays first recurrence onset. (Kanski's 10th edition)

7. Differential Diagnosis

Condition	Key Distinguishing Feature
Sarcoidosis	ACE level, serum lysozyme, bilateral hilar adenopathy; "candle wax" retinal periphlebitis
Syphilis	Serological tests (VDRL, TPHA, FTA-ABS)
Toxoplasmosis	Focal retinochoroiditis adjacent to scar; IgG/IgM serology
Serpiginous choroiditis (idiopathic)	Geographic spread from disc, no response to ATT
Eales disease	Young males, peripheral retinal periphlebitis, vitreous haemorrhage; IGRA positive in many
Viral uveitis (CMV, HSV, VZV)	Viral serology; aqueous PCR
Lymphoma (PVRL)	Vitreous biopsy; IL-10/IL-6 ratio

8. Complications

Complicated cataract (steroid-induced or inflammatory)
Secondary glaucoma (trabecular blockage, posterior synechiae → seclusio pupillae → iris bombé)
Macular scarring, CMO → permanent visual loss
Retinal detachment (exudative or tractional)
Vitreous haemorrhage → opacification
Phthisis bulbi (end-stage)
Optic atrophy

9. Summary Table — Ocular TB at a Glance

Feature	Key Points
Organism	M. tuberculosis (rarely M. bovis, atypical mycobacteria)
Mechanism	Haematogenous spread + hypersensitivity
Most common segment	Posterior (choroid) in developing countries; anterior (uveitis) also very common
Pathognomonic sign	Miliary choroidal tubercles (in miliary TB)
Specific posterior sign	Serpiginoid choroiditis tracking retinal vessels
Diagnostic test of choice (ocular fluid)	PCR for M. tuberculosis
Systemic test (preferred in BCG-vaccinated)	IGRA (QuantiFERON-TB Gold)
Treatment duration	Minimum 9 months (ATT)
Dangerous drug side effect	Ethambutol optic neuropathy; Rifabutin uveitis
Steroids	Use WITH ATT cover only

References:

Kanski's Clinical Ophthalmology: A Systematic Approach, 10th Edition, pp. 497–500
Wills Eye Manual, 8th Edition — Retinal Periphlebitis / Uveitis sections
Tintinalli's Emergency Medicine — Miliary TB, Choroidal Tubercles

This is a shared conversation. Sign in to Orris to start your own chat.