What are the key differences in diagnosis and treatment between orbital cellulitis and preseptal cellulitis in a patient presenting with eyelid swelling, redness, and pain?

Orbital vs Preseptal Cellulitis: Critical Distinctions and Management

Immediate Clinical Differentiation

The fundamental distinction is anatomic: preseptal cellulitis is confined anterior to the orbital septum and can often be managed outpatient with oral antibiotics, while orbital cellulitis involves structures posterior to the septum and requires immediate hospitalization with IV antibiotics due to risk of vision loss, cavernous sinus thrombosis, and death. 1

Key Distinguishing Features

Preseptal cellulitis presents with:

• Diffuse periorbital erythema, edema, warmth, and tenderness without clear borders 2
• Normal extraocular movements 2
• No proptosis 2
• Preserved vision and normal pupillary response 2
• Swelling and tenderness throughout the eyelid and surrounding tissues 2

Orbital cellulitis presents with:

• Proptosis (exophthalmos) 1
• Restricted and painful extraocular movements or ophthalmoplegia 1
• Vision changes or decreased visual acuity 1
• Diplopia 3
• Often associated with sinusitis (78% of cases) 3
• Fever more common (82% vs 52% in preseptal) 3

Clinical Predictors of Orbital Involvement

High-risk features requiring immediate imaging:

• Age >3 years 1
• High neutrophil count 1
• C-reactive protein >120 mg/L (highly predictive of orbital cellulitis with median CRP of 136 mg/L vs 18 mg/L in preseptal) 3
• Gross periorbital edema 1
• Absence of infectious conjunctivitis 1
• Previous antibiotic therapy without improvement 1
• Preexisting sinusitis (present in 78% of orbital cases vs 2% of preseptal) 3

Diagnostic Algorithm

When to Image

Obtain CT orbits with IV contrast immediately if ANY of the following are present:

• Proptosis, impaired extraocular movements, or decreased visual acuity 1
• Eyelid >50% closed preventing adequate eye examination 2
• No improvement after 24-48 hours of antibiotics 2
• Clinical findings cannot reliably distinguish preseptal from orbital cellulitis 2
• Systemic signs of toxicity 2

CT orbits with IV contrast is the first-line imaging with 97% accuracy for detecting complications including subperiosteal abscesses, orbital abscesses, bone erosion, cavernous sinus thrombosis, and intracranial extension 1

MRI head and orbits with and without contrast should be obtained when intracranial complications are suspected or multiple cranial nerve palsies are present 1

Critical Examination Components

Assess specifically for:

• Proptosis measurement comparing to contralateral eye 1
• Extraocular movements in all directions—pain with movement indicates postseptal involvement 1
• Visual acuity testing 1
• Pupillary response 1
• Cranial nerves II, III, IV, and VI to detect orbital apex syndrome or cavernous sinus thrombosis 1

Treatment Protocols

Preseptal Cellulitis Management

Outpatient treatment (mild cases without systemic signs):

• High-dose oral amoxicillin-clavulanate 2
• Mandatory reassessment within 24-48 hours 2

Hospitalization required if:

• Eyelid >50% closed 2
• Systemic signs present 2
• Inability to adequately examine the eye 2
• Extremes of age (infants) 4

Inpatient treatment:

• IV broad-spectrum antibiotics: amoxicillin-clavulanate, cefazolin, or ceftriaxone 2, 4
• Treatment duration 7-14 days total with transition to oral once improved 4

Orbital Cellulitis Management

Immediate hospitalization with:

• IV broad-spectrum antibiotics covering Staphylococcus aureus, Streptococcus species, and anaerobes 1
• Urgent ophthalmology and otolaryngology consultation 1
• Serial examinations monitoring for progression 4

Surgical drainage indicated if:

• Subperiosteal or orbital abscess identified on imaging 1
• Failure to improve with IV antibiotics 3
• Progressive vision loss or ophthalmoplegia 1

Notably, 71% of orbital cellulitis cases with abscesses can be managed with IV antibiotics alone, avoiding surgery in many cases with prompt treatment 3. However, 27-49% still require surgical intervention 3, 5.

Life-Threatening Complications to Prevent

Catastrophic complications of orbital cellulitis include:

• Retinal artery occlusion causing permanent vision loss 1
• Cavernous sinus thrombosis (potentially fatal) 1
• Superior ophthalmic vein occlusion 1
• Optic nerve injury 1
• Intracranial extension: meningitis, brain abscess, subdural empyema 1
• Mortality rates of 50-80% if invasive fungal sinusitis in immunocompromised patients 1

Critical Pitfalls to Avoid

Never assume all periorbital swelling is preseptal cellulitis—this delays diagnosis of orbital cellulitis requiring urgent intervention 2. Any proptosis, impaired extraocular movements, decreased visual acuity, or ophthalmoplegia indicates orbital involvement requiring immediate imaging 2.

Do not miss non-infectious mimics: Idiopathic Orbital Inflammatory Syndrome (IOIS) and IgG4-related orbital disease present similarly but require corticosteroids rather than antibiotics 1. These are diagnoses of exclusion after imaging rules out infection 1.

Bilateral ophthalmoplegia suggests cavernous sinus involvement rather than isolated orbital disease and requires immediate vascular imaging 1.

Multiple ipsilateral cranial nerve palsies (III, IV, VI) strongly suggest orbital apex or cavernous sinus pathology requiring immediate advanced imaging 1.