What are the key differences in presentation between preseptal cellulitis and orbital cellulitis?

Differentiating Preseptal from Orbital Cellulitis

Preseptal cellulitis is confined to the eyelids and tissues anterior to the orbital septum with periorbital swelling but normal eye function, while orbital cellulitis involves structures posterior to the septum and presents with proptosis, painful or limited extraocular movements, and potential vision loss—distinguishing these is critical as orbital cellulitis is a medical emergency requiring immediate intervention. 1, 2, 3

Key Clinical Distinguishing Features

Preseptal Cellulitis Presentation

• Eyelid involvement only: Periorbital erythema, edema, warmth, and tenderness confined to tissues anterior to the orbital septum 1, 2
• Normal eye function: No proptosis, normal extraocular movements, and preserved visual acuity 2
• Younger age: Mean age approximately 3.9 years 4
• Lower fever rate: Present in approximately 51.5% of cases 4
• Etiology: Most commonly from percutaneous trauma, skin breaks, or dacryocystitis 2, 5
• Sinusitis uncommon: Present in only 2% of preseptal cases 4

Orbital Cellulitis Presentation

• Proptosis: Forward displacement of the globe is a hallmark feature 6, 3
• Ophthalmoplegia: Limitation or pain with extraocular movements 6, 1, 3
• Vision changes: Decreased visual acuity indicating posterior involvement 1, 3
• Older age: Mean age approximately 7.5 years 4
• Higher fever rate: Present in approximately 82.2% of cases 4
• Sinusitis predominant: Present in 77.8% of orbital cases, particularly ethmoid sinusitis 3, 4

Laboratory and Imaging Differentiation

Laboratory Markers

• C-reactive protein: Median CRP significantly higher in orbital cellulitis (136.35 mg/L) versus preseptal cellulitis (17.85 mg/L) 4
• CRP threshold: A CRP >120 mg/L strongly suggests orbital involvement 4
• White blood cell count: Higher neutrophil counts associated with orbital cellulitis 6, 7
• Erythrocyte sedimentation rate: Significantly elevated in orbital versus preseptal cellulitis 7

Imaging Indications and Modalities

• CT orbits with IV contrast: The most useful imaging modality to differentiate preseptal from orbital cellulitis and identify complications such as subperiosteal abscess, superior ophthalmic vein thrombosis, or cavernous sinus thrombosis 6, 1, 3
• When to image: Clinical features suggesting orbital involvement, inability to adequately examine the eye due to severe swelling, failure to improve with antibiotics within 24-48 hours, or when clinical examination cannot reliably distinguish between the two entities 1, 2
• MRI orbits: Complementary to CT when more detailed assessment of intraorbital spread or intracranial complications is needed 6, 2
• Imaging NOT routinely needed: Most preseptal cellulitis cases are diagnosed clinically without imaging 2

Risk Factors for Progression to Orbital Cellulitis

The American College of Radiology identifies specific risk factors that should heighten suspicion for orbital involvement 6, 2:

• High neutrophil count 6, 2
• Absence of infectious conjunctivitis 6, 2
• Gross periorbital edema 6, 2
• Age >3 years 6, 2
• Previous antibiotic therapy 6, 2

Critical Pitfalls to Avoid

• Assuming all periorbital swelling is preseptal: Proptosis and limitation of extraocular movements are not always accurate indicators, and clinical examination alone may fail to differentiate postseptal inflammation from abscess 6
• Delaying imaging when indicated: When clinical features cannot reliably distinguish between the two entities, obtain CT orbits with contrast immediately to prevent vision-threatening complications 1, 2
• Missing intracranial complications: Orbital cellulitis can progress to subdural empyema or cavernous sinus thrombosis, requiring urgent recognition 6, 3
• Inadequate follow-up: Even presumed preseptal cellulitis requires mandatory reassessment within 24-48 hours to detect progression 1

Management Implications

• Preseptal cellulitis: Outpatient oral antibiotics (high-dose amoxicillin-clavulanate) for mild cases without systemic signs, with close follow-up 1
• Orbital cellulitis: Immediate hospitalization with intravenous broad-spectrum antibiotics; 49% require surgical drainage for abscess formation 8
• Corticosteroids: Preferred in orbital cellulitis (73.3% of cases) versus preseptal cellulitis (8.6% of cases) 4