What is the appropriate treatment for acute conjunctivitis based on the most likely etiology?

Treatment of Acute Conjunctivitis

The appropriate treatment for acute conjunctivitis depends primarily on distinguishing between viral, bacterial, and allergic etiologies, with viral conjunctivitis requiring only supportive care, bacterial conjunctivitis benefiting from topical antibiotics in moderate-to-severe cases, and allergic conjunctivitis responding to topical antihistamines with mast cell-stabilizing activity. 1

Immediate Red-Flag Assessment

Before initiating treatment, urgently refer to ophthalmology if any of the following are present:

• Visual loss or decreased vision 2, 3
• Moderate to severe pain (beyond mild irritation) 2, 3
• Corneal involvement detected by fluorescein staining (opacity, infiltrate, ulceration, or dendritic lesions) 1, 2, 3
• Severe purulent discharge suggesting gonococcal infection, which can cause corneal perforation within 24-48 hours 2, 3
• Recent ocular surgery or trauma 3
• History of herpes simplex virus eye disease 2, 3
• Immunocompromised state 2, 3
• Neonatal conjunctivitis (any purulent discharge is an emergency until gonococcal/chlamydial causes are excluded) 2
• Contact lens wear with conjunctivitis (risk of bacterial keratitis) 3

Diagnostic Approach by Clinical Features

Viral Conjunctivitis (Most Common Overall)

Clinical presentation:

• Watery discharge with follicular reaction on inferior tarsal conjunctiva 1, 2, 3
• Preauricular lymphadenopathy 1, 2, 3
• Often sequentially bilateral (starts unilateral, becomes bilateral within days) 1, 3
• Concurrent upper respiratory symptoms (rhinorrhea, sore throat, fever) 1, 3
• Subconjunctival hemorrhages, chemosis, eyelid swelling may be present 1, 3
• Absence of matted eyelids on waking 4

Treatment:

• Do NOT prescribe topical antibiotics – they provide no benefit and cause unnecessary toxicity 1, 2, 3, 4
• Supportive care only: preservative-free artificial tears 4-6 times daily, cold compresses 2, 3, 4, 5
• Self-limited course: resolves within 5-14 days 1, 3
• Infection control: strict hand hygiene with soap and water, avoid sharing towels/pillows, no eye rubbing, avoid close contact for 10-14 days from symptom onset 2, 3
• Causative virus remains infectious on surfaces for up to 28 days – emphasize environmental cleaning 3

Follow-up:

• Return if symptoms persist beyond 2-3 weeks or worsen 3
• Severe cases with pseudomembranes or corneal involvement require re-evaluation within 1 week 3

Bacterial Conjunctivitis

Clinical presentation:

• Mucopurulent or purulent discharge with matted eyelids on waking 1, 2, 3, 4
• Papillary (not follicular) conjunctival reaction 1, 3
• Lack of itching 4
• Unilateral or bilateral 1
• Preauricular lymphadenopathy less common unless hypervirulent organism 3

Treatment algorithm:

Mild cases:

• Often self-limited, resolving in 1-2 weeks without treatment 1, 4, 6
• Delayed antibiotic prescribing is preferred: provide prescription but advise waiting 2-3 days before filling if symptoms don't improve 2, 5
• Topical antibiotics shorten duration by approximately 3-4 days and allow earlier return to school/work 2, 4, 6

Moderate to severe cases:

• Prescribe 5-7 day course of broad-spectrum topical antibiotic 1, 2, 3
• No single antibiotic is superior – choose most convenient or cost-effective option 1, 2, 3:
  • Polymyxin B/trimethoprim drops 4 times daily 7, 8, 6
  • Erythromycin ointment 4 times daily 3
  • Fluoroquinolones (e.g., besifloxacin 0.6%, moxifloxacin 0.5%) 3 times daily 3, 9

Treatment failure:

• If no improvement after 5-7 days, obtain conjunctival cultures and susceptibility testing before changing antibiotics 3

Special Bacterial Pathogens Requiring Systemic Therapy

Gonococcal conjunctivitis:

• Hyperacute presentation: marked eyelid edema, copious purulent discharge, severe bulbar injection 2, 3
• Emergency requiring hospitalization for parenteral antibiotics PLUS topical therapy 2, 3
• Can cause corneal perforation within 24-48 hours if untreated 2
• Daily follow-up until resolution, treat sexual contacts 3
• Consider in sexually active adults and neonates 3-5 days old 2

Chlamydial conjunctivitis:

• Follicular conjunctivitis with distinctive follicles on bulbar conjunctiva and semilunar fold 2
• Topical antibiotics alone are inadequate – requires systemic antibiotics 2, 3, 4
• Evaluate and treat sexual contacts 3
• In neonates, appears 5-19 days after birth and associated with pneumonia in 50% of cases 2

Allergic Conjunctivitis

Clinical presentation:

• Itching is the hallmark symptom 2, 3, 4
• Bilateral involvement 3
• Watery discharge with mild mucous component 3
• History of atopy, asthma, eczema, or seasonal pattern 3
• Absence of preauricular lymphadenopathy and matted eyelids 3

Treatment:

• First-line: topical antihistamines with mast cell-stabilizing activity 2, 3, 4, 5:
  • Olopatadine 0.1-0.2% twice daily 3
  • Ketotifen 0.025% twice daily 3
• Environmental modifications: wear sunglasses as allergen barrier, cold compresses, refrigerated artificial tears, avoid eye rubbing 3
• Allergen avoidance: hypoallergenic bedding, minimize outdoor exposure during high pollen counts 3
• Refractory cases: short 1-2 week course of topical corticosteroids with ophthalmology follow-up 3

Herpes Simplex Virus (HSV) Conjunctivitis

Clinical presentation:

• Usually unilateral (bilateral in atopic/immunocompromised patients) 1, 2
• Bulbar conjunctival injection, watery discharge, mild follicular reaction 1, 2
• Distinctive signs: vesicular rash or ulceration on eyelids, dendritic epithelial keratitis on fluorescein staining 1, 2
• Palpable preauricular node 1, 2

Treatment:

• Mild conjunctivitis without corneal involvement: often self-limited, resolves in 4-7 days 1, 2
• With corneal involvement (dendritic keratitis):
  • Topical ganciclovir 0.15% gel 3-5 times daily (less toxic than trifluridine) 1
  • OR topical trifluridine 1% solution 5-8 times daily (causes epithelial toxicity if used >2 weeks) 1
  • PLUS oral antivirals: acyclovir 400 mg 5 times daily, valacyclovir 500 mg 2-3 times daily, or famciclovir 250 mg twice daily 1
• AVOID topical corticosteroids – they potentiate HSV epithelial infections 1, 3
• Follow-up within 1 week with visual acuity and slit-lamp examination 1
• Neonates require immediate pediatric consultation – systemic HSV is life-threatening 1

Varicella Zoster Virus (VZV) Conjunctivitis

Clinical presentation:

• Vesicular dermatomal rash or ulceration of eyelids 1, 2
• Unilateral or bilateral bulbar injection, watery discharge, follicular reaction 1
• May have limbal or conjunctival vesicles 1

Treatment:

• Topical antibiotics to prevent secondary bacterial infection of necrotic vesicles 1
• Oral antivirals for persistent/recalcitrant disease in immunocompetent patients: acyclovir 800 mg 5 times daily for 7 days, valacyclovir 1000 mg every 8 hours for 7 days, or famciclovir 500 mg 3 times daily for 7 days 1
• Immunocompromised patients require more aggressive treatment 1
• Caution with renal impairment 1

Molluscum Contagiosum

Clinical presentation:

• Shiny, dome-shaped umbilicated lesion(s) on eyelid skin or margin 1
• Typically unilateral follicular conjunctivitis with punctate epithelial keratitis 1
• Multiple/large lesions in adults suggest immunocompromised state 1, 2

Treatment:

• Incision and curettage (aggressive enough to cause bleeding), simple excision, excision with cautery, or cryotherapy 1
• Identify and treat nascent lesions to reduce recurrence 1
• Conjunctivitis may require weeks to resolve after lesion removal 1

Critical Pitfalls to Avoid

• Never prescribe topical corticosteroids indiscriminately – they prolong adenoviral infections, worsen HSV infections, increase intraocular pressure, and cause cataracts 1, 2, 3
• Do not miss gonococcal conjunctivitis – it causes corneal perforation and requires immediate systemic treatment 2, 3
• Always examine the cornea with fluorescein staining in any purulent conjunctivitis to detect early corneal involvement 2
• Avoid chronic use of topical vasoconstrictors – causes rebound vasodilation 3
• Consider sexual abuse in children with gonococcal or chlamydial conjunctivitis 2
• Contact lens wear must be discontinued during any infectious conjunctivitis 3