In a 2½‑year‑old child with conjunctival redness and eyelid edema, what is the most likely diagnosis and how should it be managed?

Bacterial Conjunctivitis with Preseptal Cellulitis

In a 2½-year-old child presenting with conjunctival redness and eyelid edema, bacterial conjunctivitis is the most likely diagnosis, and you should initiate topical antibiotic therapy immediately while carefully ruling out preseptal cellulitis and examining for corneal involvement with fluorescein staining. 1, 2

Immediate Assessment Priorities

Perform fluorescein staining immediately to detect corneal involvement, which would require urgent ophthalmology referral. 1, 2 Look specifically for:

• Purulent or mucopurulent discharge (suggests bacterial etiology) 1, 3
• Severity of eyelid edema and erythema (mild suggests simple conjunctivitis; marked swelling with warmth suggests preseptal cellulitis) 4
• Presence of proptosis or impaired extraocular movements (would indicate orbital cellulitis requiring immediate CT imaging) 2
• Fever and systemic symptoms (41% of preseptal cellulitis cases present with fever) 4
• Unilateral vs bilateral involvement (bacterial conjunctivitis can be either; preseptal cellulitis is typically unilateral) 1, 4

Most Likely Diagnosis: Bacterial Conjunctivitis

At 2½ years old, the most common bacterial pathogens are Haemophilus influenzae (most prevalent), Streptococcus pneumoniae, and Moraxella catarrhalis. 5, 3 Clinical features supporting this diagnosis include:

• Purulent discharge with "sticky eyes" on awakening 3
• Bulbar conjunctival injection 1
• Foreign body sensation 3
• Possible concomitant otitis media (the "conjunctivitis-otitis syndrome" occurs in up to 30% of cases with H. influenzae) 5

Critical Red Flags Requiring Immediate Ophthalmology Referral

Do not delay referral if any of these are present: 1, 2

• Visual loss or moderate-to-severe pain
• Severe, rapidly reaccumulating purulent discharge
• Corneal involvement on fluorescein examination
• Proptosis or impaired extraocular muscle function
• No improvement after 3-4 days of appropriate antibiotic treatment

Treatment Algorithm

First-Line Management

Initiate topical broad-spectrum antibiotic drops immediately (polymyxin B/trimethoprim is effective against H. influenzae, S. pneumoniae, S. aureus, and Pseudomonas). 6, 3 Dosing: instill 1 drop every 4-6 hours for 7-10 days. 3

Consider oral antibiotics if: 5

• Concomitant otitis media is present or suspected
• Severe bilateral involvement
• Age <6 years with high risk of developing otitis media

Oral antibiotics are superior to topical therapy alone in preventing the development of otitis media in the conjunctivitis-otitis syndrome. 5

If Preseptal Cellulitis is Suspected

When eyelid edema is marked with warmth, erythema, and tenderness (present in 19.9% of cases), preseptal cellulitis must be considered. 4 Initiate systemic antibiotics immediately:

• Most commonly used regimens include clindamycin (72.8% of cases) or ceftriaxone (54.4% of cases), either alone or in combination 4
• Obtain CT imaging if: proptosis, impaired extraocular movements, or severe systemic toxicity are present 2
• Risk factors include recent sinusitis (10.3% have concurrent ethmoid sinusitis), odontogenic infection, insect bites, or periocular trauma 4

Common Pitfalls to Avoid

Do not miss gonococcal conjunctivitis: Though rare at this age, if discharge is severe and rapidly reaccumulating, treat as presumptive gonococcal infection with immediate systemic antibiotics and ophthalmology referral, as corneal perforation can occur within 24-48 hours. 1, 2, 7

Do not assume viral etiology without proper assessment: While adenoviral conjunctivitis is common, it typically presents with watery (not purulent) discharge, preauricular lymphadenopathy, and often bilateral involvement with a prodrome of upper respiratory symptoms. 2, 7, 8

Do not overlook examination of the internal ear: In children with bacterial conjunctivitis, consider referral for otoscopic examination given the high association with acute otitis media. 1, 5

Do not continue antibiotics beyond 48 hours without improvement: If no response after 24-48 hours of appropriate therapy, refer to ophthalmology to rule out resistant organisms, chlamydial infection, or alternative diagnoses such as ligneous conjunctivitis (which can mimic preseptal cellulitis). 1, 9

Infection Control and Return to Daycare

The child remains infectious until 24-48 hours after starting appropriate antibiotic treatment. 10 Counsel parents on:

• Hand hygiene before and after touching the child's eyes 1, 10
• Use of separate towels and washcloths 10
• Child should not attend daycare until 24 hours of antibiotic therapy completed 10