What is the likely cause of yellow eye discharge in an otherwise healthy infant with a white sclera and no signs of illness?

Nasolacrimal Duct Obstruction

The most likely diagnosis is congenital nasolacrimal duct obstruction (CNLDO), which affects over 5% of infants and presents with yellow mucoid discharge and excessive tearing in an otherwise healthy infant with a white sclera. 1

Clinical Presentation and Diagnosis

The key distinguishing features that point to CNLDO rather than infectious conjunctivitis include:

• Yellow or ropy mucous discharge without signs of systemic illness 1
• White sclera (no conjunctival injection) - this is critical, as bacterial conjunctivitis would show bulbar conjunctival injection 2
• Persistent tearing (epiphora) that appears shortly after birth or during the first weeks of life 3, 1
• Discharge that accumulates in the conjunctival sac, particularly after sleep 1

CNLDO is the most common cause of persistent tearing in children younger than 1 year 3. The obstruction occurs at the distal end of the nasolacrimal duct, causing tears and mucus to accumulate rather than drain properly 4.

Critical Red Flags to Rule Out

Before assuming benign CNLDO, you must exclude serious conditions:

• Purulent (not just mucoid) discharge requires immediate evaluation to rule out gonococcal or chlamydial conjunctivitis, which are emergencies in neonates that can cause septicemia, meningitis, and death 5
• Conjunctival injection (red eye) suggests infectious conjunctivitis rather than simple duct obstruction 2
• Bluish swelling over the nasolacrimal sac indicates dacryocystocele, which requires urgent ophthalmology referral due to high infection risk 3
• Erythema, warmth, and tenderness over the lacrimal sac suggests acute dacryocystitis, requiring immediate treatment to prevent orbital cellulitis, meningitis, or sepsis 3

Management Approach

Conservative management is appropriate for uncomplicated CNLDO:

• Observation with nasolacrimal massage is first-line treatment, as spontaneous resolution occurs in approximately 90% by age 6 months and more than 99% by age 12 months 3
• Topical antibiotics are reserved only for secondary bacterial conjunctivitis (when conjunctival injection develops) 1
• Referral to ophthalmology should be deferred until at least 6-9 months of age for persistent symptoms 3

When to Treat as Bacterial Conjunctivitis

If the infant develops true bacterial conjunctivitis (conjunctival injection with purulent discharge), treatment becomes necessary:

• Bacterial conjunctivitis remains infectious until 24-48 hours after starting appropriate antibiotic treatment 6
• Warning signs requiring immediate referral include: severe purulent discharge that rapidly reaccumulates, corneal involvement, moderate to severe eye pain, or no improvement after 3-4 days of antibiotic treatment 6

Common Pitfall

The most common error is treating simple CNLDO with antibiotics when no conjunctival injection is present. The yellow discharge alone, without red eye or systemic illness, does not warrant antibiotic therapy 1.