What is the treatment for unilateral conjunctivitis (pink eye)?

Treatment of Unilateral Conjunctivitis (Pink Eye)

For unilateral conjunctivitis, initiate a 5-7 day course of broad-spectrum topical antibiotic (such as moxifloxacin 0.5% three times daily) while maintaining high suspicion for viral, herpetic, or serious bacterial etiologies that require different management. 1

Initial Assessment and Red Flags

The unilateral presentation is clinically significant and demands careful evaluation:

• Bacterial conjunctivitis typically presents with mucopurulent discharge and matted eyelids upon waking 2, 3
• Viral conjunctivitis (especially HSV) commonly presents unilaterally with watery discharge, follicular reaction, and may have preauricular lymphadenopathy 4
• Neoplastic or serious conditions often present unilaterally with intense bulbar injection and may mimic chronic unresponsive conjunctivitis 4

Critical warning signs requiring immediate ophthalmology referral include: visual loss, moderate-to-severe pain, severe purulent discharge, corneal involvement, lack of response after 3-4 days, recurrent episodes, history of HSV eye disease, or immunocompromised status 1, 2

Treatment Algorithm by Etiology

Presumed Bacterial Conjunctivitis (Most Common Initial Treatment)

First-line therapy:

• Apply topical fluoroquinolone (moxifloxacin 0.5%, levofloxacin, or gatifloxacin) 3-4 times daily for 5-7 days 1, 5
• Alternative: bacitracin ophthalmic ointment 1-3 times daily for 5-7 days 2
• Topical antibiotics provide earlier clinical remission (62% cured by days 3-5 vs 28% with placebo) and faster bacterial eradication (71% vs 19%) 1, 6

If no improvement after 3-4 days:

• Obtain conjunctival cultures and Gram stain 1
• Consider MRSA, especially in nursing home patients or community-acquired infections 1
• Consider chlamydial or gonococcal infection requiring systemic therapy 1

Gonococcal Conjunctivitis (Requires Systemic Treatment)

This is a medical emergency with risk of corneal perforation if untreated 1:

• Adults: Ceftriaxone 250 mg IM single dose PLUS azithromycin 1 g oral single dose 1
• Neonates: Ceftriaxone 25-50 mg/kg IV or IM single dose 1
• Requires daily monitoring until resolution 1
• Screen for concurrent genital infections and treat sexual partners 1
• Consider sexual abuse in children 1, 7

Chlamydial Conjunctivitis (Requires Systemic Treatment)

Topical therapy alone fails because Chlamydia trachomatis causes intracellular infection 1:

• Adults: Azithromycin 1 g oral single dose OR doxycycline 100 mg oral twice daily for 7 days 1
• Neonates/Infants: Erythromycin base or ethylsuccinate 50 mg/kg/day oral divided in 4 doses for 14 days 1
• More than 50% of infected infants have infection at other sites, necessitating systemic treatment 1
• Screen for concurrent genital infections and treat sexual partners 1

Viral Conjunctivitis

Adenoviral conjunctivitis (most common viral cause):

• No proven effective antiviral treatment 1, 8
• Supportive care: Refrigerated preservative-free artificial tears 4 times daily, cold compresses, topical antihistamines for symptom relief 1
• Avoid topical antibiotics due to potential adverse effects and no benefit 1
• Self-limited with improvement within 5-14 days 4
• Strict hand hygiene with soap and water; avoid close contact for 7-14 days 1

HSV conjunctivitis (critical to identify):

• First-line: Topical ganciclovir 0.15% gel OR topical trifluridine 1% solution 1
• Alternative/Adjunct: Oral antivirals (acyclovir, valacyclovir, or famciclovir) 1
• NEVER use topical corticosteroids without antiviral coverage as they potentiate HSV infection 1
• Prolonged trifluridine use (>2 weeks) causes epithelial toxicity 1
• Usually subsides within 4-7 days unless complications occur 4

Allergic Conjunctivitis

If bilateral itching develops or allergic etiology suspected:

• First-line: Second-generation topical antihistamines with mast-cell stabilizing properties 1
• Adjunctive measures: Cold compresses, refrigerated preservative-free artificial tears, sunglasses as allergen barrier 1
• If symptoms persist: Brief 1-2 week course of low-potency topical corticosteroids with monitoring of intraocular pressure 1

Common Pitfalls to Avoid

• Delayed recognition of gonococcal conjunctivitis leads to corneal perforation and vision loss 1
• Using corticosteroids in HSV conjunctivitis without antiviral coverage potentiates infection 1
• Indiscriminate antibiotic use in viral conjunctivitis causes unnecessary toxicity 1
• Failure to consider sexual abuse in children with gonococcal or chlamydial conjunctivitis 1, 7
• Missing unilateral presentation as a red flag for HSV, neoplasia, or serious bacterial infection 4

Follow-Up and Monitoring

• Return for evaluation if no improvement after 3-4 days of appropriate treatment 7, 2
• If symptoms persist despite therapy, obtain conjunctival cultures to rule out MRSA 2
• Complete resolution typically occurs within 7-10 days with appropriate treatment 2
• Educate about hand hygiene, avoiding eye touching, using separate towels, and discarding eye makeup 1, 7