How can viral and bacterial acute conjunctivitis be differentiated in a child?

Differentiating Viral from Bacterial Conjunctivitis in Children

The most reliable clinical discriminators are discharge character and eyelid matting: bacterial conjunctivitis presents with purulent or mucopurulent discharge that causes sticky, matted eyelids upon waking, while viral conjunctivitis typically produces watery discharge with minimal matting. 1, 2

Key Clinical Features for Differentiation

Bacterial Conjunctivitis – Hallmark Signs

• Purulent or mucopurulent discharge (green or yellow) that mats the eyelids, especially on waking, is the cardinal feature distinguishing bacterial from viral etiology 1, 3
• History of "gluey" or "sticky" eyelids combined with physical findings of mucoid or purulent discharge has a 96% positive predictive value for bacterial infection 2
• Bilateral presentation is typical, though it may initially affect one eye before spreading 1
• Bulbar conjunctival injection (red eye) is present but less specific 1, 2
• The condition is predominantly caused by nontypeable Haemophilus influenzae (82%), Streptococcus pneumoniae (16%), and Staphylococcus aureus (2%) in children 2

Viral Conjunctivitis – Distinguishing Characteristics

• Watery discharge is the predominant feature, with minimal to no purulent component 1, 3
• Follicular reaction on the inferior tarsal conjunctiva (requires lid eversion to visualize) is highly suggestive of viral etiology 4, 1
• Preauricular or periauricular lymphadenopathy is commonly present and strongly favors viral infection 4, 1
• Often begins unilaterally but becomes sequentially bilateral within days 1, 5
• Associated symptoms include burning, gritty sensation, and concurrent upper respiratory infection or recent exposure to infected contacts 1, 3
• Adenovirus accounts for the majority of viral cases, presenting as pharyngoconjunctival fever (fever, pharyngitis, bilateral conjunctivitis) 1

Critical Examination Steps

Mandatory Assessment Components

• Fluorescein staining must be performed in every case to detect corneal involvement, which indicates more serious disease requiring immediate ophthalmology referral 4, 1, 6
• Eyelid eversion to examine the tarsal conjunctiva for follicles (viral) versus papillae (bacterial or allergic) 4
• Palpation of preauricular lymph nodes – enlargement strongly suggests viral etiology 4, 1
• Visual acuity testing to identify vision-threatening complications 1, 5

Red-Flag Features Requiring Immediate Referral

• Marked eyelid edema with copious purulent discharge suggests gonococcal conjunctivitis, which can cause corneal perforation within 24-48 hours 1, 6
• Vesicular lesions on eyelids are pathognomonic for herpes simplex virus and require urgent ophthalmology referral 1, 6
• Positive fluorescein staining indicating corneal involvement 1, 6
• Visual changes, moderate-to-severe pain, or lack of improvement after 24-48 hours of appropriate therapy 1, 5

Practical Diagnostic Algorithm

Step 1: Assess Discharge Character

• Purulent/mucopurulent + matted lids → Bacterial conjunctivitis 1, 2
• Watery discharge + minimal matting → Viral conjunctivitis 1, 3

Step 2: Examine for Follicles and Lymphadenopathy

• Follicular reaction + preauricular lymphadenopathy → Viral conjunctivitis 4, 1
• Absence of follicles + purulent discharge → Bacterial conjunctivitis 1, 2

Step 3: Perform Fluorescein Staining

• Positive staining → Immediate ophthalmology referral regardless of etiology 4, 1
• Negative staining → Proceed with etiology-specific management 1

Step 4: Check for Associated Symptoms

• Fever, pharyngitis, upper respiratory infection → Viral (adenoviral pharyngoconjunctival fever) 1
• Concurrent otitis media → Bacterial (add oral antibiotics) 6

Special Considerations in Neonates

• Any purulent conjunctivitis in a neonate is an emergency until gonococcal and chlamydial causes are ruled out 1, 6
• Gonococcal conjunctivitis appears within the first week of life with marked eyelid edema and copious purulent discharge; can progress to septicemia, meningitis, and death 1, 6
• Chlamydial conjunctivitis presents between 5-19 days of age with purulent or mucopurulent discharge (follicles are absent in neonates) 1, 6
• Cultures are mandatory in all cases of neonatal conjunctivitis 4

Common Diagnostic Pitfalls

• Assuming absence of discharge excludes infection – early viral conjunctivitis may have minimal watery discharge that is easily missed 5
• Relying solely on physician gestalt – subjective clinical scoring has only 50.6% accuracy compared to 96% accuracy when using specific clinical criteria (gluey lids + purulent discharge) 2
• Failing to perform fluorescein staining – corneal involvement may not be clinically apparent without staining 4, 1
• Not everting the eyelid – follicles on the tarsal conjunctiva are a key diagnostic feature of viral conjunctivitis but require lid eversion to visualize 4, 1

Management Implications

• Bacterial conjunctivitis: Topical antibiotics shorten symptom duration and facilitate earlier return to school/work; delayed prescribing (wait 2-3 days if no improvement) is preferred for uncomplicated cases since most resolve spontaneously within 1-2 weeks 1
• Viral conjunctivitis: Supportive care with cool compresses; most cases self-resolve within 5-14 days; mandatory follow-up in 3-4 days to assess for complications 1, 5
• Cultures are rarely cost-effective in routine conjunctivitis but are indicated for recurrent, severe, chronic purulent cases, or when treatment fails 4