Posner-Schlossman Syndrome vs. Typical Anterior Uveitis
Posner-Schlossman syndrome differs fundamentally from typical anterior uveitis by presenting with markedly elevated intraocular pressure (often >40 mmHg) accompanied by paradoxically mild or minimal anterior chamber inflammation, whereas typical anterior uveitis shows prominent inflammation with normal or only modestly elevated IOP.
Key Distinguishing Features
Clinical Presentation
Posner-Schlossman Syndrome:
- Dramatic IOP elevation (frequently >40 mmHg in 44% of cases) 1
- Minimal inflammation: No flare in 56% and no cells in 53% of cases 1
- Unilateral presentation in middle-aged males (mean age 42 years) 2, 1
- Recurrent attacks with symptom-free intervals 2
- Few keratic precipitates (78.5% have KPs, but they are sparse) 1
- Preserved visual acuity (>0.5 in 80.3% of eyes) 1
- Stromal iris atrophy without posterior synechiae 3
- Absence of macular edema and retinitis 3
Typical Anterior Uveitis:
- Normal or modestly elevated IOP 4
- Prominent anterior chamber inflammation with cells and flare
- Can be bilateral
- More sustained inflammation requiring ongoing treatment
- Posterior synechiae formation common
- Risk of macular edema
- May require systemic immunosuppression 5
Pathophysiology
The critical difference lies in etiology: Posner-Schlossman syndrome is primarily caused by cytomegalovirus (CMV) infection in 50-65% of cases 3, 1, 6, representing a localized viral reactivation rather than autoimmune inflammation. This explains the disproportionate pressure elevation relative to inflammation—the trabecular meshwork dysfunction from viral infection causes severe IOP spikes without the robust inflammatory response seen in autoimmune uveitis.
Diagnostic Approach
For PSS, specifically look for:
- Unilateral presentation in a middle-aged male (particularly Filipino-Chinese ethnicity, as Asian populations show higher incidence) 7
- IOP >40 mmHg with minimal AC cells/flare
- Few, fine keratic precipitates
- Open angle on gonioscopy 2
- PCR testing of aqueous humor for CMV-DNA (positive in 50.6-65.5% of cases) 1, 6
Avoid the pitfall: The mild inflammation may be missed initially, leading to misdiagnosis as acute angle-closure glaucoma 8. Always perform gonioscopy to confirm open angles.
Treatment Differences
Posner-Schlossman Syndrome requires:
- Topical antiviral therapy (ganciclovir) as primary treatment 9
- Topical corticosteroids for inflammation control 9
- Aqueous suppressants for IOP management 2
- Systemic antivirals (valganciclovir) may be needed for recurrent cases 10
Typical Anterior Uveitis requires:
- Topical corticosteroids as primary therapy (prednisolone acetate 1%) 11
- Cycloplegic agents 4
- Systemic immunosuppression (methotrexate, biologics) if requiring >1-2 drops/day of steroids for >2-3 months 11
- No role for antivirals unless herpetic etiology confirmed
Prognostic Implications
PSS carries specific risks:
- Secondary glaucoma from recurrent IOP spikes and trabecular damage 7
- Corneal endothelial cell loss 3
- Glaucomatous optic neuropathy if untreated 7
- Cataract formation 3
The recurrent nature means long-term monitoring is essential, but synechiae formation and macular edema are typically absent 3, unlike typical anterior uveitis where these complications are common.
Quantitative Iris Assessment
Recent evidence shows SS-AS-OCT can objectively differentiate PSS from other anterior uveitis syndromes through iris stromal thickness and optical density measurements 6, providing an additional diagnostic tool when clinical features overlap.